Nineteen-Day Fast to be the one foretold by the Báb, accepted the fast, but altered many of its details and regulations. The Bahá'í fast resembles fasting practices of several other religions. Lent is a period of fasting for Christians, Yom Kippur and many other holidays for Jews, and the fast of Ramadan is practiced by Muslims. The Bahá'í fasting most resembles the fast of Ramadan, except that the period of fasting is defined as a fixed Bahá'í month, whereas Muslims fast during a lunar month, whose specific Gregorian dates vary from year to year. Bahá'u'lláh established the guidelines of the fast in
Fast of the Firstborn not hear the completion of the tractate, or if he does not understand what he hears, or if he is in the "shiva" period of mourning and is thus forbidden from listening to the Torah material being taught, some authorities rule that subsequent eating would not qualify as a "seudat mitzvah" and he would therefore be forbidden to break his fast. Other authorities allow a firstborn to break his fast under such circumstances. The "Minchas Yitzchak" (ibid.) suggests that a firstborn in such a position should at least try to contribute to the "siyum" in some way, such as by