Exodus 13:3-8

Then Moses said to the people, “Commemorate this day, the day you came out of Egypt, out of the land of slavery, because the LORD brought you out of it with a mighty hand. Eat nothing containing yeast. Today, in the month of Aviv, you are leaving. When the LORD brings you into the land of the Canaanites, Hittites, Amorites, Hivites and Jebusites—the land he swore to your ancestors to give you, a land flowing with milk and honey—you are to observe this ceremony in this month: For seven days eat bread made without yeast and on the seventh day hold a festival to the LORD. Eat unleavened bread during those seven days; nothing with yeast in it is to be seen among you, nor shall any yeast be seen anywhere within your borders. On that day tell your son, ‘I do this because of what the LORD did for me when I came out of Egypt.’