Fasting in the Old Testament

Fasting in the Old Testament was a religious ritual that could be practised both individually and collectively.

Reasons to Fast

A period of fasting could serve to reinforce, or serve as a sign of a number of different things:

A sign of mourning: one example is David who fasted after the deaths of Saul and Jonathan (2 Samuel 1:12), and the death of Abner (2 Samuel 3:35).
Penance: Daniel fasted to atone for his people’s sins (Daniel 9:3).
To reinforce a personal prayer: in Psalm 35:13, the psalmist hopes that fasting will cause his prayer to be answered by God.
A sign of devotion to God: in early Judaism fasting was a sign of piety, just as prayer and giving alms to the poor.

In the Old Testament, a few occasions for public fasting are mentioned:

The Day of Atonement is the only day specified in the Torah as a time for everyone to fast. In this way, the Israelites atone for the sins they have committed (Leviticus 16:29; in the Good News Bible, “On the tenth day of the seventh month the Israelites and the foreigners living among them must fast and must not do any work”).
Particularly in the period after the exile, more and more annual gatherings emerged at which people would fast. Zechariah mentions four days of fasting (Zechariah 8:19; see also Ezra 8:21-23; Nehemiah 9:1).
People also fasted during Purim. This tradition is linked to the story of how the Jews were rescued from being persecuted by Haman. Before the festival can be celebrated, there first needs to be a day of fasting, in imitation of Esther Esther 4:16.