According to Exodus 12, the Israelites were to eat unleavened bread for seven days during the Passover festival.
The instruction formed part of the Israelites’ departure from Egypt. They were told to remove leaven from their houses and eat unleavened bread from the evening of the fourteenth day of the first month through the twenty-first day. The lack of leaven reflects the hurried departure described in the narrative.
Exodus also presents the seven-day period as a lasting observance. The first and seventh days were designated as sacred assemblies, with restrictions on ordinary work. Later Jewish practice developed additional details, calendars, and customs around Passover.
This seven-day period should not be confused with the single Passover meal or with the seven-day festival of Unleavened Bread as described in later Jewish terminology. Both are closely connected in Exodus.