MI SHE-BERAKH (Heb. מִי שֶׁבֵּרַךְ; "He Who Blessed"), initial words of a prayer formula said on various occasions and invoking God's blessing on the community and on individuals.
During the Sabbath morning service after the Torah reading a blessing is invoked "May He who blessed our forefathers… bless this holy congregation…" The wording of this Mi she-Berakh varies in the various rites, but in its essence can be found in the oldest manuscripts. In different communities there are various additional Mi she-Berakh prayers, e.g., for one who does not interrupt his prayers from *Barukh she-Amar through the *Amidah, for one who always comes on time to the synagogue, etc. In Israel there is a Mi she-Berakh for the soldiers of the Israel Defense Forces. A personal Mi she-Berakh is generally recited for every person called to the reading of the law sometimes specifying the donation being made to the synagogue. If the person called to the Torah is celebrating a special occasion, such as his bar mitzvah, forthcoming marriage, or the birth of a child, the prayer is worded so as to make reference to the event. For a female child the name is usually given in the prayer. The usual Mi she-Berakh starts with the words "May He who blessed our fathers Abraham, Isaac, and Jacob bless…," however, when the blessing is invoked for a sick female or one recovering from childbirth, the names of the matriarchs, Sarah, Rebekah, Rachel, and Leah are added to the invocation. It is also customary to recite relevant versions of the prayer at banquets celebrating events of religious importance.
Eisenstein, Dinim, s.v.