There are several customs that are observed during the month of Elul, and their purpose is to inspire each person to amend his actions and sincerely repent.

Sephardic communities begin to recite Selihot (penitential prayers) as early as the day after Rosh Hodesh Elul, as detailed below. Ashkenazic communities start to sound the shofar every morning after prayers, from the first of Elul until the twenty-eighth of the month. On the day before Rosh HaShana, the shofar is not sounded.

At the end of the prayer service, Psalms 27 is added, which begins with the words: “By David. The Lord is my light and my salvation.” This psalm deals with various aspects of approaching God while expressing complete trust in Him, as well as a longing to be in His shadow. It also contains an allusion to the upcoming festivals of Tishrei, including Sukkot, and therefore one continues to recite the psalm daily until the last day of Sukkot, which is Hoshana Rabba. Among Sephardic and hasidic communities, the psalm is recited following the morning and afternoon services, whereas Ashkenazic communities say it after the morning and evening services.

According to the Lubavitch custom, which dates back to the time of Rabbi Israel Ba’al Shem Tov, three chapters from the book of Psalms are added after every morning service in the month of Elul, starting from the second day of Rosh Hodesh, which is the first of Elul. On the first day, one says Psalms 1–3, on the second day Psalms 4–6, and so on. One continues to recite the psalms in order throughout the Ten Days of Repentance as well, and on the Day of Atonement one says nine psalms before Kol Nidrei, nine before going to bed, nine after the Musaf prayer, and nine after Ne’ila. One thereby completes the entire book of Psalms.

During the month of Elul, it is customary to recite penitential prayers called Selihot. These are liturgical poems and verses that focus on one’s remorse for the wrongdoings that he has performed in the past year, while asking forgiveness from God. There are two main sections recited between the liturgical poems:

(1) God’s Thirteen Attributes of Mercy, from Exodus 34:6-7 (“The Lord, the Lord, God, merciful and gracious, slow to anger and abounding in kindness and truth, etc.”), which Moses invoked when he prayed for the children of Israel after the sin of the Golden Calf, and which evoke God’s forgiveness when they are recited with a full heart.

(2) The “confession,” a list of various sins that helps us recall and regret our misdeeds.

There are different customs among the various communities with regard to Selihot: Among the Sephardim, it is customary to start saying them from the second day of Elul. The formula of Selihot throughout the month is fixed, but a few liturgical poems are added during the Ten Days of Repentance, from Rosh HaShana until Yom Kippur. The Selihot are commonly recited in song and verse. In some communities it is customary to sound the shofar when saying the Thirteen Attributes of Mercy.

Ashkenazim begin saying Selihot on a Saturday night toward the end of the month of Elul. When Rosh HaShana falls on a Thursday or Saturday, they start to say Selihot on the last Saturday night of the year. But if Rosh HaShana falls on a Monday or Tuesday, the Selihot are begun a week earlier, on the previous Saturday night, which means that the period of Selihot before Rosh HaShana lasts for a week and a half. The structure of the Selihot and their main sections remains the same throughout the period, but the individual liturgical poems change daily. Some recite the formula of the “confession” three times each day, while others recite it once. On the eve of Rosh HaShana, the Selihot are lengthier than on the other days.

The preferred time to recite Selihot is between the middle of the night and dawn. If one cannot say Selihot during that time frame, or if he failed to do so, one may recite Selihot before the morning prayer service, or at any point throughout the day. If there is no other choice, one may say Selihot even at night before midnight. One should keep in mind that according to Jewish chronology, a day starts from the preceding night, which means that the Selihot that are recited at night belong to the following day.

Further reading: For more on Shabbat, see A Concise Guide to the Torah, pp. 6, 174, 192, 226; A Concise Guide to the Sages, p. 275; A Concise Guide to Mahshava, p. 33.