The 7th of Adar (which this year will be March 1st 2012) marks the Yartzheit of Moshe Rabbenu, and there is a custom among many to observe a fast on this day. The custom to fast on 7 Adar is mentioned already by Maran in the Shulhan Aruch (Orah Haim 580:2). The rationale behind this custom is the fact that it is customary to fast on the Yartzheit of one’s primary Rabbi, as the Mishna Berura (Rabbi Yisrael Meir Kagan, 1839-1933) cites (in 568:46) from the Shela (Rabbi Yeshayahu Horowitz, 1558-1630). The Mishna Berura explains that one is obligated to honor his Rav Mubhak (primary Rabbi) even more so than his parent, and thus just as it is customary to fast on a parent’s Yartzheit, it is appropriate to fast on the Yartzheit of one’s Rabbi, as well. Moshe Rabbenu is, without question, the Rav Mubhak of the entire Jewish people, and it is therefore appropriate to observe a fast on his Yartzheit, 7 Adar.
It goes without saying that merely refraining from food and drink is not as important as praying and studying Torah, which are the primary means of Teshuba. Therefore, it is proper on 7 Adar for communities to assemble for Torah classes in observance of this special day. The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), in the introduction to his Tikkun (service) for 7 Adar, writes that it is also customary to light candles in memory of Moshe Rabbenu on this day.
There is a special custom for the Hevra Kadisha (benevolent society) of every community to observe 7 Adar together as a Ta’anit Sibur (communal fast day). They recite Selihot, wear Tefillin at Minha, and conduct the standard Ta’anit Sibur prayer service. Then, after the fast, they have a meal together. The Hevra Kadisha members observe this fast as atonement in case they were neglectful in their sacred duty to give proper respect to the deceased. The Yartzheit of Moshe Rabbenu was chosen as the appropriate occasion for this observance because his burial site remains unknown ("Ve’lo Yada Ish Et Keburato" – Debarim 34:6).
Although the fast of 7 Adar is mentioned in the Shulhan Aruch, it is nevertheless preferable to declare a formal acceptance of the fast the previous day, just as is done before a voluntary private fast. If one makes a formal acceptance the day before the fast, he can then add the paragraph of "Anenu" in the Amida on the fast day. The acceptance should be declared on the afternoon of the day before the fast, at the end of the Amida of Minha, just before "Oseh Shalom." The Mishna Berura (562:27) writes that this should preferably be done at Minha Ketana – meaning, during Minha recited in the late afternoon, as opposed to early Minha (Minha Gedola). Certainly, the acceptance should not be made before Minha, and if it is made before Minha, it is ineffective.
The proper text of the acceptance, as printed in many Siddurim, based upon the Hid"a (Rav Haim Yosef David Azulai, 1724-1807) in his work Moreh Be’esba (3:186), is, "Hareni Mekabel Alai Ta’anit Yahid Me’alot Ha’shahar Ad Set Ha’kochavim" – "I hereby accept upon myself a private fast from daybreak until nightfall." It is important that one accept the fast of 7 Adar as a private fast (Ta’anit Yahid), and not a communal fast (Ta’anit Sibur). The acceptance is valid even if it was made silently, in one’s mind (Shulhan Aruch, Orah Haim 562:6). One should not add the words "Beli Neder" or "Beli Kabala," because he indeed intends to formally accept the fast upon himself. However, one may add a stipulation that he accepts the fast only on condition that he has the physical strength to observe the fast, and that if he feels unable to complete the fast, he will recite the chapter of Tehillim "Mizmor Le’David Hashem Ro’i" and will then be allowed to eat.
If one did not make the acceptance during Minha, he may still accept the fast until sundown, and even after sundown, during the period of Ben Ha’shemashot.
If one knows that observing a fast will adversely affect the quality of his prayers, or hamper his ability to study Torah properly, then it is preferable not to fast so that he could pray and study to the best of his ability. Similarly, it is improper to fast if this would cause one to feel arrogant and superior to other people. Humility and proper study and prayer are for more valuable than fifty fast days. Therefore, if observing this fast will have an adverse effect on these or other areas of Torah observance, it is far preferable not to observe the fast. Certainly, though, 7 Adar is a very significant day that should be commemorated as such in all communities.
