That ye shall say, it is the sacrifice of the Lord's passover,.... This lamb is a sacrifice, both eucharistical, or by way of thanksgiving for their safety, when the firstborn of the Egyptians were slain, and for their deliverance out of Egypt; and also propitiatory, the blood of this lamb being a propitiation or atonement for all within the house where it was sprinkled, as before observed from Aben Ezra; and typical of the atoning sacrifice of Christ our passover, 1Co 5:7 and this was commanded by the Lord, and approved of and accepted by him, and therefore called his sacrifice as well as passover, for the following reason:who passed over the houses of the children of Israel, when he smote the Egyptians, and delivered our houses; their families, not suffering the destroying angel to enter into them, which was a very distinguishing mercy, and worthy of remembrance.
Now in this they were to instruct their children in successive generations, that the memory of it might be kept up, and a sense of the goodness of God continued, and his name glorified. Maimonides says,"it is a command to make this known to children, even though they do not ask it, as it is said, "and thou shall show thy son", Ex 13:8.
According to the son's knowledge, his father teaches him; how if he is a little one or foolish? he says to him, my son, all of us were servants, as this handmaid, or this servant, in Egypt; and on this night the holy blessed God redeemed us, and brought us into liberty: and if the son is grown up, and a wise man, he makes known to him what happened to us in Egypt, and the wonders which were done for us by the hand of Moses our master, all according to the capacity of his son; and it is necessary to make a repetition on this night, that the children may see, and ask, and say, how different is this night from all other nights!
until he replies and says to them, so and so it happened, and thus and thus it was:''and the people bowed the head and worshipped; signifying the deep sense they had of the mercy shown them, their thankfulness for it, and their readiness to observe the ordinance now instituted.
Hilchot Chametz Umetzah, c. 7. sect.