Exodus 13:8

And thou shall show thy son in that day ,.... On the first of the days of the feast of unleavened bread, the reason of eating it; and this is to be shown not to a son or single child only, but by parents to all their children, sons and daughters, and even unasked, as Maimonides F2 Hilchot Chametz Umetzah, c. 7. sect. 2, 3. interprets it; and so Jarchi's note is, to a son that knows not how to ask or what to ask about; see Gill on Exodus 12:26 , Exodus 12:27 ,

saying, this is done because of that which the Lord did unto me, when I came forth out of Egypt : that is, this unleavened bread is eaten because of the quick and speedy deliverance of Israel out of Egypt, so that they had not time to leaven their dough.