No leavened bread was to be eaten by the Hebrews for seven days in commemoration of their hasty escape from Egypt (see Exodus 12:17–20). In later biblical history, the Feast of Unleavened Bread is used in reference to the covenant obligation of purging corruption after celebrating redemption.
6 And on the fifteenth day of the same month is the Feast of Unleavened Bread to the LORD; for seven days you shall eat unleavened bread.