Exodus 13:6-8

13:6 For seven days you must eat bread made without yeast, and on the seventh day there is to be a festival to the Lord. 13:7 Bread made without yeast must be eaten for seven days; no bread made with yeast shall be seen among you, and you must have no yeast among you within any of your borders.

13:8 You are to tell your son on that day, ‘It is because of what the Lord did for me when I came out of Egypt.’