גדר מנהג ישראל תורה

In a previous article, we offered a critical analysis of a popular סגולה for easy childbirth, namely to bite the פיטם of an אתרוג. Some responded to me that, although (as we showed there) this practice makes little sense and has little (if any) grounds in הלכה (and common sense), we should yet maintain this practice because of the principle of מנהג ישראל תורה.

In this article we cite a number of instances where this principle appears in halachic literature and see if this principle can reasonably be applied here as well or not.

1

There is an איסור to read documents on שבת. To this end, the בח prohibits a waiter from reading a list of guests at a meal. The מ"א [1] disagrees, saying that מנהג ישראל תורה and that חשבונות של מצוה are allowed.

2

בני יששכר has a lengthy מאמר on the מנהג of decorating ספרי תורה with flowers on שבועות, which he begins with the premise of מנהג ישראל תורה [2].

3

בני יששכר has a brief מאמר in which he explains the מנהג ישראל תורה of wearing costumes on פורים, based on המן's גזירה being a punishment for the Jews having bowed to נבוכדנצר's statue only prima facie; so too הקב"ה only "pretended" to make a גזירה. To this end, we wear costumes so that the identity of the wearer is only pretend. [3]

4

מטה אפרים brings a מנהג to make large candles that will stay lit the entire יו"כ on ערב יו"כ. There is an additional מנהג to daven while making the candles. מטה אפרים says not to make fun of or stop this מנהג, as מנהג ישראל is תורה [4].

5

פרי צדיק refers to eating fruits on טו בשבט as מנהג ישראל תורה [5].

6

האלף לך שלמה references מנהג ישראל תורה as a reason why he is opposed to machine מצה, namely because מנהג ישראל תורה that מצה is round, whereas machine מצה is square. [6]

7

לקוטי תורה has a lengthy Kabbalistic explanation as to why the מנהג ישראל תורה is not to dip מצה in salt, as one normally would do for their לחם משנה [7].

8

There were those who used to plant לולבים and הדסים in flowerpots in their homes. ערוה"ש offers halachic reasoning to the effect that these plantings were fit for use, followed by saying that מנהג ישראל תורה and people are behaving correctly. [8]

9

שפת אמת refers to חביטת הערבה as a מנהג ישראל תורה.

10

שפת אמת gives a lengthy and deep explanation as to the reason for פורים costumes, which he refers to as a מנהג ישראל תורה [10].

11

ערוה"ש observes that the ברכה on הפרשת חלה is להפריש חלה מן העיסה, as opposed to להפריש תרומה מן העיסה; and although it is not מעכב, still, מנהג ישראל תורה and, as such, the מנהג needs to be explained, which ערוה"ש immediately proceeds to do. [11]

12

בני יששכר gives a number of deeply kabbalistic reasons for various מנהגי אבלות that are practiced during ספירה, referring to them as מנהג ישראל תורה [12].

13

There are a number of מנהגים relating to the מוצאי שבת service for which various reasons are given. There are those who are מגמגם on these מנהגים; however, מנהג ישראל is תורה [13].

14

In general, the meaning of מנהג ישראל תורה is that there are lessons in יראת שמים and עבודה to be learned even from מנהגי ישראל, although they are not necessarily a חיוב originating in שס ופוסקים [14].

Conclusion

Nowhere (that I have found) is מנהג ישראל תורה used to mean, "there is a מנהג doesn't make any sense, but we should do it anyway, because מנהג ישראל תורה". Rather, the phrase is exclusively used to mean that while there is often no source for a particular מנהג in classical halachic and Talmudic reasoning, still, there is often an extra-halachic reason, such as a lesson to reinforce or the like, and, as such, the מנהג should still be kept.

Practically, this means that a מנהג that has a valid reason should be kept, even where it is not a חיוב per se, whereas a מנהג that does not make sense should not be kept. [15]

[1] שז:יז

[2] סיון ד:ז:א. This is brought down להלכה by כף החיים או"ח תצד:נט:א. See also בני יששכר סיון ד:ח:ה

[3] אדר ט:א. For an additional reason, see שם שם:ב:א

[4] תרג:ז

[5] לטו בשבט, ג:א

[6] השמטות לב, יא

[7] ויקרא ה, סו

[8] או"ח תרמה:כא

[9] דברים, לסוכות כב:ח; וע"ע שם טו:ד

[10] ויגש, ח:ו

[11] יו"ד שכח:ב

[12] ניסן יב:ח:א

[13] ערוה"ש או"ח רצה:א

[14] based on טעמי המנהגים תתעו:ד

[15] One may say that it doesn't hurt. Indeed, in Chelm they used to wear glasses without lenses because, after all, it doesn't hurt.

מנהג אכילת וופלים בחנוכה

Recently I discovered a מנהג to eat waffles on חנוכה. The origin of this מנהג is that 'ה made נס ופלא during these days. To this end, a מנהג developed in Amsterdam to eat vaffeles (Belgian waffles).

This מנהג was later mentioned in a song written by Moshe Yehuda Piza (see also here) which describes all the food-related מנהגים that are practiced throughout the year.

Sources:

https://www.shearithisrael.org/prayer/liturgy/minor-holidays/ (heading: Ahaba Be'taanugim)

https://www.youtube.com/watch?v=zSqa0NL-FJo (at approx. 24 mins.)

Postscript: perhaps one can eat the waffles with dairy syrup or the like, thereby fulfilling both מנהגים at once.

נשיכת הפיטם כסגולה ללידה קלה

There is a מנהג that a woman who is expecting a child bites a פיטם as a סגולה for an easy childbirth. In this article we will present the source and reason behind this custom and examine its legitimacy.

The earliest source for this idea is the נזיר שמשון quoting a(n anonymous) manuscript, in which the following was written:

"Expectant women have a custom that on הושענא רבה (after their husbands return home from shul) to take [1] the פיטם of the אתרוג (the reason for this being that there is an opinion that the fruit of the עץ הדעת was an אתרוג [2]), and they give money to the poor so that הקב"ה should save them and their baby from death.

They then say the following תפלה:

רבון העולם בשביל חוה שהיא אכלה מעץ הדעת - אותו החטא הוא שגרם מיתה בעולם. ואם הייתי באותו מקום לא הייתי אוכלת ולא הייתי נהנית ממנו, כמו שלא רציתי לפסול אתרוג זה בשבעת ימי החג שעברו, והיום שפסלתי אין בו מצוה. וכשם שיש לי הנאה בפיטם זה כן הייתי נהנית לראות עץ הדעת שאמר הקב"ה לאדם וחוה שלא לאכול ממנו ולא הייתי עוברת את ציוויו, ותקבל ברצון את תפלתי ואת תחנתי שלא אמות מלידה זו. ותושיעני לילד בנחת ובלי צער, ולא יהיה שום נזק לי או לולדי כי אתה האל המושיע

Translation (mine):

Master of the World, because חוה ate from the עץ הדעת therefore death was caused to exist in the world. If I were in her place, I wouldn't have eaten or benefited from it, just as I did not want to פסל this אתרוג during the seven days of יו"ט that just passed by, and today that I did פסל it - there is no מצוה to be done with it anymore. And just as I have pleasure from [eating] this פיטם - so would I have had pleasure from [only] seeing the עץ הדעת that הקב"ה told אדם and חוה not to eat from; and I wouldn't have transgressed His command. In this merit You should accept my תפלה and תחנה - that I should not die from this birth - graciously. Please save me such that I can give birth easily, without pain, and that there shouldn't be harm to me or to my child - for You are the L-rd Who saves."

We will now proceed to enumerate a number of problems inherent in this מנהג:

1) In the original תפלה (found in אלף המגן תרס:ו), there are numerous grammatical mistakes and instances of faulty sentence structure (which I have edited out for easier reading).

2) While there is an opinion that the עץ הדעת was an אתרוג tree, this does not account at all for those opinions which disagreed [2]. Moreover, even if the עץ הדעת was an אתרוג tree, the connection between that fact and biting the פיטם - and not any other part of the fruit - is not entirely clear.

3) To assert that, had one been in חוה's place, one would not have partaken of the עץ הדעת is wildly presumptuous at the very least, and even seems to be full-blown גאוה and עזות; how any sane, rational person could sincerely believe such a statement is not clear.

4) The subject of the תפלה attempts to prove that they would not have committed the חטא עץ הדעת by showing that they did not פסל the אתרוג the entire יו"ט. This is ludicrous as there was no specific temptation to do so, in which case one has a difficult time indeed making this a line of advocacy on their own behalf.

5) The assertion that פסלing an אתרוג on הושענא רבה does not interfere with the מצוה is inaccurate, as the entire day one can still fulfill the מצוה, so the אתרוג still has a use at that point.

6) The subject asserts that she has pleasure from the פיטם. What pleasure is referred to here is unclear, as פיטם doesn't necessarily taste like anything in particular.

7) The assumption of the תפלה seems to be that death from childbirth is a frequent occurrence בר מנן. Today, however, this is not the case 'בחסדי ה.

8) In general, the entire category of סגולות is suspect, [3] as the psychology behind a סגולה is an attempt at forcing G-d's Hand. To this end, the only סגולות that certainly have authentic validity are those that are reliably sourced, which brings us to our next point: one may counter that this סגולה is found in אלף המגן, a reliable source of פסק הלכה.

דרכי חיים ושלום, however, [4] contends that this entire paragraph (which is, in fact, copy-pasted from חיים וברכה אות רכח quoting נזיר שמשון) did not appear in the early editions of אלף המגן, rather it seems to have crept in at some later point, in which case this סגולה does not carry the אלף המגן's stamp of approval.

Conclusion

Biting a פיטם as a סגולה for an easy childbirth would seem to be not much more than an old wives' tale that has no clear basis in הלכה ומנהג and, as such, should be frowned upon.

Appendix

There are those who countered to me, in my discussion of the topic with them, that מנהג ישראל תורה, and, as such, one should keep this (or any) מנהג even where it does not make sense. Although the entire premise of this claim is not palatable to the logical mind, we will בעז"ה address this important principle in a future article.

The information in this article was compiled with the research assistance of members of the Sofrim Google group for writers.

[1] While the specific instructions are only to take, rather than bite, the פיטם, presumably the purpose of taking the פיטם is to then eat it - as is evinced from the accompanying תפלה in which experiencing pleasure from the פיטם plays a role.

[2] בראשית רבה פרשה טו אות ז

[3] For more on this point, see here. Note: the sentiments or opinions held by that author (in that article and elsewhere) are solely his own; I am only מציין to that article specifically as it expresses my point clearly.

[4] אות תשצו. See also מקור חיים סי' תרסד who is also critical of this מנהג.

My Visit to Shearith Israel

Over the past חול המועד my wife and I had the occasion to visit Congregation Shearith Israel, the Spanish and Portuguese synagogue on the Upper West Side of Manhattan, for Minha/Arbit. In this post I will present a brief report of my observations there.

We arrived a few minutes early, with some time to get acquainted with our surroundings and settle in. We were given special חול המועד editions of their Book of Prayers (edited by R David de Sola Pool and first published by the Union of Sephardic Congregations in 1941), which had, in the inside of the front cover, an instructions page pasted, as well as a few minor additions throughout the book.

The Hazzan began the afternoon service with Psalm 84 (Tehilim are chanted before and after each service, thereby grounding the service in Biblical literature), which was chanted aloud by the Hazzan, with the congregation chiming in at specific points. (At this point the Hazzan sits on a bench facing his Reader's Desk, also called a Tebah, which is on a platform a few feet above the floor; the railing around the platform has long candlesticks that are lit at every service - originally to provide actual light but today just pro forma [1].)

The Hazzan then rose to begin Ashre, which was largely chanted aloud by the Hazzan, with the congregation chiming in at specific points.

The beginning (until האל הקדוש) and ending (from רצה until המברך את עמו ישראל בשלום) sections were chanted aloud by the Hazzan, with the congregation reading along in a whisper, except in certain places where they were expected to chime in, such as מודים, the beginning of which is chanted by the congregation with the Hazzan in unison. [2]

Alenu (of which only the first paragraph is said at all) was chanted in unison by the congregation with the Hazzan, to this tune.

The same pattern, more or less, was used for the evening service (preceded by Psalm 134 and concluding with Psalm 121) with the exception of the Hazzan chanting the Amidah aloud, which is not done at the evening service.

Following the evening service we had dinner in the Elias Room (a side room used as a Bet Midrash) sucah. This room is used all year for classes and the like. Before Sucot the roof is raised by a hydraulic system and the opening is covered with sekhakh [3].

On our way out we took a few pictures which we are happy to share with you:

above: Dutch chandelier, reflecting architectural tastes of the congregation's founders

above: fresh citrus fruits to keep away insects, doubling as succah decorations; facing is the remainder of the Elias room, which functions as a bet midrash and kiddush room

above: corn, used as a succah decoration, representing the food of America

above: the Small Sanctuary, used on weekdays; this room is meant to be a replica of the original synagogue built in 1730

above: talets (plural for talet, see here) and prayer books

above, background: hat gemach (one may only be called to the Torah on Shabbat and Festivals if one is properly attired in a hat, jacket and tie; in case one does not have a hat, there is a gemach to suit a variety of styles and tastes); foreground: displays used for various periodic exhibitions

I must add that, in general, the congregants were very kind and welcoming. We are looking forward to our next opportunity to visit.

[1] The congregation's current building was built in 1897, before electric power was commonplace. The entire building relied on candlelight until the 1920s, where electric power was installed.

Interestingly, the Portuguese synagogue in Amsterdam (also called the Esnoga - considered the mother synagogue of the Spanish-Portuguese congregations worldwide) as well as Bevis Marks (considered the mother synagogue of the Spanish-Portuguese congregations in England) still use candlelight to this day. (Some have commented to me that this phenomenon is in consonance with the concept of צורת הישיבה, in that an institution has a distinct character which needs to be preserved even in the appurtenances of its physical structure.)

[2] This is also done for מוסף on Shabbat and Festivals, the only difference being that מוסף is chanted aloud in its entirety.

The reason for this practice seems to be that, in the case of מנחה, people tend to be in a rush to get back to work and, in the case of מוסף, to finish the already-long service, so the early Western Sephardic rabbis established a Minhag that, for these services, the Hazzan should chant the entire Amidah aloud, with the congregation following along quietly.

[3] This was originally built with a mechanical system that needed to be cranked up, which is still done at the Esnoga.

חזי מאי עמא דבר

Some may wish to invoke the principle of חזי מאי עמא דבר (see what people do) in the case of daily ברכת כהנים, namely that it is wrong to attempt to reinstate daily ברכת כהנים where this was not previously practiced, because there is a rule that we have "see what people do" and follow the מנהג as such.

In this article we will search the halachic literature for some examples of where this principle is applied or not.

1

There is a question in the [1] 'גמ what ברכה ראשונה to make where מזונות, העץ, or האדמה are not made. The תנא קמא says שהכל.

רבי טרפון says בורא נפשות רבות וחסרונן.

רבא בר רב חנן asked either אביי or רב יוסף what the הלכה is; he was answered to see what people do.

2

Normally, one does not answer אמן after one's own ברכה. There is a צד in the 'גמ, however, that אמן should be said after certain ברכות [2].

תוספות observes, as a conclusion, that if we look at what people do, we will see that they only say אמן after בונה ירושלים in ברכת המזון.

3

Some had a מנהג to write various פסוקים in their מזוזות, in addition to the obligatory פרשיות.

מעשה רקח [3] says that the consensus of all the פוסקים is not to add anything, and indeed this is supported by the fact that this is what (most) people do.

4

The רשבא writes in a תשובה [4] that in some communities there is a מנהג that on ליל ראש חודש between חצי קדיש and שמונה עשרה of מעריב, the שמש announces "ראש חודש". This is not a הפסק because it is a צורך התפלה, so that people should remember it is ראש חודש and say יעלה ויבא. This is what people do, and no one has ever protested.

5

All the פוסקים mention that המפיל should be said with שם ומלכות. However, some סדורים print it without שם ומלכות, although none of the פוסקים make explicit mention of such a possibility. This being the case, we revert to the principle of seeing what people do only where the הלכה is רופפת בידך; where the הלכה is clear-cut, however, the fact that we have not seen this הלכה kept is not a proof of its non-applicable status. [5]

6

The רשבא has another תשובה [6] in which he discusses whether or not to make קידוש by the 3rd סעודה on שבת. He barely even weighs the pros and cons of the issue before saying "look what people do - no one makes קידוש at the 3rd סעודה".

7

In general, רב פעלים [7] points out that in order for what people do to have any weight, their מנהג must be known and certain.

8

אדמת קודש [8] presents a שאלה as to where to make a ברכה on putting up a מזוזה. After reaching a conclusion, he says that "this is all להלכה ולא למעשה, and in practice, if the הלכה is unclear, one should see what people do".

9

כף החיים [9] presents a discussion as to whether or not one may shecht birds sitting. He concludes to see what people do.

10

The רמא [10] has a dilemma as to whether one שמש is sufficient for an entire household to not be considered benefitting from the light of נר חנוכה, or if each individual מנורה requires its own independent שמש. He concludes that his observation of common practice is for each individual מנורה to have its own שמש, after which he then supports his conclusion with halachic reasoning.

Conclusion

חזי מאי עמא דבר is a halachic principle that, like all halachic principles, applies in some places and not in others. It is up to the the discretion of פוסקים where to apply it or where not.

In general, it seems that פוסקים apply this principle in cases where the הלכה is not clearly established, at which point we observe the practice of the general population, by which we can assume that the common practice is based on a פסק that was accepted widely. [11]

There is a clear-cut הלכה that ברכת כהנים must be done daily, no ifs, ands or buts [12]. This הלכה is definite, certain, established, and undisputed. There are a variety of attempted justifications why not to but none of them hold much halachic water (see here). This is a far cry from רופפת בידך. Even the פוסקים who offer reasons why not to such that, according to their reasoning, ברכת כהנים is nearly an איסור (see, for example, here), hold that, in theory, we are מחוייב only that there are factors mitigating our התחייבות in practice. No one (not even the בית אפרים, who uses every possible justification to prop up the מנהג) apply this principle of חזי מאי עמא דבר to ברכת כהנים; so why should we?

Appendix

Logic would dictate a few caveats:

1) The people that we observe should be generally religiously learned and knowledgeable, by which we can assume that their halachic behavior has halachic import, and is not simply based on error or ignorance.

2) This entire rule only applies where the הלכה is not clear-cut and established. If it is - even where said הלכה is not commonly followed - then too bad on what people do; they must be taught to improve their halachic behavior.

3) If the הלכה is not initially established, at which point a פוסק may decide to follow the מנהג, said פוסק (or any other פוסק) may then decide to clarify the הלכה based on objective criteria and straightforward halachic reasoning, at which point the הלכה would become clear, and relying on the מנהג may no longer be permitted or necessary.

[1] ברכות מד.

שיטה מקובצת and ריטבא there point out that this is indeed how we pasken, in that we say שהכל before and בורא נפשות after. See ב"י או"ח רד:יא

ערבי נחל (בראשית ב:כח), however, has a deeper understanding of this 'גמ. He asks a very obvious question: why didn't רבא or רב יוסף say the הלכה explicitly? Why does he pin the matter on the מנהג? Can there never be such a thing as a מנהג טעות? (Ed. - This is a rhetorical question: there obviously can be; people are not perfect and, as such, are capable of making mistakes. For a fuller treatment of מנהג טעות, see here.)

This can be explained as follows:

All the creations were created by mechanism of a specific דיבור, such as "יהי אור". Hence ברכות הנהנין tend to focus on creation, for example, בורא פרי העץ or בורא פרי האדמה. On the other hand, water was created automatically through the very act of 'ה speaking, so the ת"ק suggests שהכל נהיה בדברו, which implies כביכול passive, as opposed to active, creation, in that speech is made (partly) through water (vapor).

Whereas רבי טרפון argues that water also was created specifically, hence בורא נפשות רבות; so where רבה בר רב חנן wanted to find out the הלכה, he was told "you can understand this point on your own by seeing מאי עמא דבר, meaning, what a person's speech consists of, namely, fire (warmth), wind (air), and water (vapor). So too הקב"ה's דיבור also consists, so to say, of fire, wind and water, which is why the הלכה follows the תנא קמא."

[2] ברכות מה:ב

[3] הל' תפילין ומזוזה וספר תורה ה:ד

[4] סימן תצג. I have seen many congregations where the גבאי announces יעלה ויבא in that exact spot.

[5] כף החיים או"ח רלט:ז:א

[6] חלק ז שנ:א

[7] חלק ד יו"ד לו:ו

[8] יו"ד יח:יב

[9] יו"ד כד:א

[10] שו"ת פא:ב

[11] פרשת דרכים טו:כד; see also אמרי בינה חלק רביעי חקרי לב ה

[12] see, for example, רמבם in the opening lines of הלכות תפלה וברכת כהנים, ספר החינוך - מצות ברכת כהנים בכל יום, and משנה תענית ד:א which presumes, as obvious, that ברכת כהנים is done daily, and simply addresses at which תפלות this דין applies.

In general, many of the דינים of ברכת כהנים are based on the presumption of its daily occurrence.

'לקט קצת מנהגי ימים נוראים - ג

A collection of various points related to the ימי הרחמים והרצון הבאים עלינו לטובה:

1

Today we will discuss a peculiar but sensible מנהג of ישיבה תורה ודעת [1] that the בעל תפלה sits for היה עם פיפיות שלוחי עמך ישראל (following עלינו in the חזרת השץ of מוסף) and a member of the congregation rises and says (or sings) the פיוט (until ואתה תשמע מן השמים) following which the בעל תפלה takes back over.

I have not seen this practiced elsewhere; however, considering the very content of this פיוט, namely a תפלה on behalf of שלוחי ציבור worldwide (and also considering that the בעל תפלה could use a well-deserved break), this indeed makes much sense and would seem to be very appropriate.

2

We mentioned last year that the תקיעות before מוסף are referred to in the halachic literature as תקיעות דמיושב (sitting תקיעות) while the תקיעות during מוסף are referred to as דמעומד (standing תקיעות). Perhaps readers will enlighten me, but I am not aware of any community that actually sits during תקיעות דמיושב. If so, why are they referred to as מיושב in the first place?

חיי אדם [2] explains that the main תקיעות are the ones that take place during מוסף. Once חזל instituted תקיעות before מוסף - which are referred to as מיושב because the congregation is still sitting as they have not yet stood up for מוסף - in order to confuse the שטן [3], so then they also instituted that these תקיעות should be done properly, with ברכות etc. - as a result of which we end up technically fulfilling our obligation with those תקיעות, so therefore we stand for those as well.

2.2

Mendy Meyer shared with me that during the תקיעות דמעומד in Breuer's the מקריא announces שברים and תרועה separately, thereby giving the תוקע a short breath. Zachary Edinger (shamash at Shearith Israel) noted that this is the Spanish-Portuguese מנהג as well. This is another interesting crossover between Western אשכנזים and Western ספרדים (a topic that I hope to explore in greater depth in the future).

[1] מנהגי ישיבה תורה ודעת, ראש השנה אות לח, וראה גם שם יום כפור אות כ. The same arrangement is practiced for ויאתיו; it is not clear to me what the specific connection is between the two פיוטים that would cause such a מנהג to be established.

[2] שבת ומועדים כלל קמב אות יז

[3] This is accomplished as follows: we do not want the שטן to prosecute us while we blow שופר during מוסף. Evidently, he thinks that this is the only time we blow; so, where he suddenly hears us blowing before מוסף - he thinks משיח must have arrived - after all, why else would we blow שופר before מוסף?! - at which point his job is finished and הקב"ה will eliminate him. (How and why the שטן hasn't caught on to our trick after so many years is beyond me - but, if חזל say the trick works, then so be it.)

The תקיעות before מוסף are still referred to as מיושב because, theoretically, one can decide to fulfill their obligation with תקיעות דמעומד exclusively, in which case they have the (theoretical) option to sit for תקיעות דמיושב. (See מ"ב תקפה:ב)

גדר מנהג מבטל הלכה

We have shown previously in this series that even though there is no fully legitimate reason not to do ברכת כהנים daily in חו"ל (or anywhere for that matter) - still, those who attempted to do so were stopped from Heaven. The question begs itself to be asked: why would great people be stopped by Heaven from doing what הלכה demands of them?

Some have suggested that perhaps this was not the right thing to do in the first place: after all, there is a principle that מנהג מבטל הלכה. -?-

In this article we will address where the aforementioned principle applies or doesn't apply, and, in the process, we will see whether it applies here or not.

1

To begin with, a Sefaria search indicates that the overwhelming majority of halachic sources that apply this principle - do so in relation to monetary matters, which are beyond the purview of this forum. This would indicate, however, that monetary matters are the primary area in which מנהג is מבטל הלכה to begin with. There are only a handful of instances where מנהג מבטל הלכה comes up in the halachic literature relating to איסור והתר. We will delineate each of them here, one by one.

2

One of the earliest sources to mention מנהג מבטל הלכה is מסכת סופרים [1], where this principle is immediately qualified by saying that "a מנהג which can be מבטל הלכה is only such a מנהג that was established by ותיקים; but a מנהג that has no proof from the תורה is not a מנהג but rather a mistake in judgment". This qualification is also codified as פסק הלכה by the מהריק (see here).

3

A full treatment of the issue is beyond the scope of this article, but אבודרהם [2] has a discussion whether or not to say ברוך ה לעולם between שומר עמו ישראל לעד and חצי קדיש in a weeknight מעריב, due to a concern of needing to juxtapose גאולה to תפלה, and ברוך ה לעולם being an interruption thereto. He concludes that "our ancestors have already accustomed themselves to saying it - and their מנהג is תורה - as we say that מנהג is מבטל הלכה".

One must observe, however, that halachic justification is offered there to do so, in that ברוך ה לעולם is תפלה, by virtue of its containing many theoretical components of שמונה עשרה. Indeed, this reasoning seems to have been adopted universally among אשכנזים (with the notable exception of the גרא and - ironically - the בעל התניא who deleted it from their respective סדורים).

4

The מאירי [3] says that מנהג is only מבטל הלכה where הלכה is מקיל and מנהג is מחמיר, or where מנהג is מקיל where there is no איסור; but if a מנהג is מקיל where there is an איסור - we don't listen to the מנהג.

Conclusion

מנהג מבטל הלכה is a halachic principle that, like many halachic principles, is not a blanket statement - that מנהג is ALWAYS מבטל הלכה - but rather, applies in some places and not in others - as in מנהג is sometimes מבטל הלכה.

Where, indeed, מנהג is מבטל הלכה is 1) in (some) monetary matters  - the details of where it does or not in this regard being beyond the scope of this forum, 2) for איסור והתר - where established by ותיקים and - where there is a מחלוקת as to what the הלכה should be, or the מנהג is more מחמיר than the strict הלכה, or where מנהג is מקיל שלא במקום איסור [4].

In addition to all that has been said so far, none of the classical פוסקים, in discussing this סוגיא, invoke מנהג מבטל הלכה at all. I would be hesitant to apply a halachic principle to a particular situation where none of the earlier פוסקים have done so.

[1] יד:יח

[2] סדר התפלות לחול - ערבית

[3] .ראש השנה טז

[4] Not to do ברכת כהנים every day is not a קולא but rather a חומרא: the פוסקים who offer reasons why not to - for example, the כהנים cannot טובל, or they are not מיוחס, or we are not happy enough, or it is a טורח הציבור that causes people to lose work etc., - all offer reasons for an איסור rather than a פטור.