The day after Rosh HaShana, the third of Tishrei, is the Fast of Gedalya. This fast was instituted to commemorate the murder of Gedalya son of Ahikam, who was the representative of the royal family left by Nebuchadnezzar king of Babylon after he destroyed the First Temple. Gedalya was appointed to lead the remnant of the people of Judah who were left in the Land of Israel. He was murdered by Ishmael son of Netanya, who vehemently opposed the relationship between Gedalya and the king of Babylon. Following the murder, all the remaining people went down to Egypt, and thus the last embers of the rule of Judah in the Land of Israel were extinguished.

The fast begins at dawn, about an hour and a half before sunrise, and ends upon the emergence of the stars. The precise times can be found in Jewish calendars.

Every male over the age of thirteen and every female over the age of twelve are prohibited to eat or drink on this day. Pregnant and nursing women generally do not observe this fast. In a case of illness, weakness, or any other difficulty in fasting, one should consult a rabbi.

Apart from the usual additions to all the prayers of the Ten Days of Repentance, there are special additions for the Fast of Gedalya.

The Selihot of the fast day are recited as on the rest of the Ten Days of Repentance, at night or at dawn. Some recite them during the morning prayers, before Tahanun.

After the repetition of the Amida by the prayer leader and the recitation of Selihot, the regular fast-day passages are read from the Torah (Exodus 32:11–14 and 34:1–10). These sections deal with Moses’ request of God to have mercy upon the children of Israel and to forgive them after the sin of the Golden Calf. This is an appropriate reading for a fast day, on which we seek God’s mercy.

Some, especially Sephardim and Hasidim, have the custom to don a prayer shawl [tallit] and tefillin for the afternoon prayer service on fast days.

After Ashrei, the Torah reading of the morning is repeated, but this time a haftara is read as well. The selection (Isaiah 55:6–56:8) opens with the phrase: “Seek the Lord when He is found,” and discusses regret for one’s sins, repentance, and requesting God’s forgiveness.

In the blessing of Shome’a Tefilla in the Amida prayer, one adds the “Answer us” [Aneinu] passage. The prayer leader adds this in his repitition of the Amida after the blessing of “Who redeems Israel.” In Israel only, during the prayer leader’s repetition of the Amida prayer, the priests recite the priestly benediction (Numbers 6:24–26) in the afternoon prayer service, just as in the morning prayers, provided that the service takes place in the late afternoon.

When the third of Tishrei falls on a Shabbat, the fast is postponed to Sunday, the fourth of Tishrei.