Exodus 13:3, 9

So Moses said to the people, “This is a day to remember forever—the day you left Egypt, the place of your slavery. Today the LORD has brought you out by the power of his mighty hand. (Remember, eat no food containing yeast.)

This annual festival will be a visible sign to you, like a mark branded on your hand or your forehead. Let it remind you always to recite this teaching of the LORD: ‘With a strong hand, the LORD rescued you from Egypt.’