21 Then Moses called all the elders of Israel together and said to them, "Go, pick out a lamb or young goat for each of your families, and slaughter the Passover animal. 22 Drain the blood into a basin. Then take a bundle of hyssop branches and dip it into the blood. Brush the hyssop across the top and sides of the doorframes of your houses. And no one may go out through the door until morning. 23 For the Lord will pass through the land to strike down the Egyptians. But when he sees the blood on the top and sides of the doorframe, the Lord will pass over your home. He will not permit his death angel to enter your house and strike you down. 24 "Remember, these instructions are a permanent law that you and your descendants must observe forever. 25 When you enter the land the Lord has promised to give you, you will continue to observe this ceremony. 26 Then your children will ask, 'What does this ceremony mean?' 27 And you will reply, 'It is the Passover sacrifice to the Lord, for he passed over the houses of the Israelites in Egypt. And though he struck the Egyptians, he spared our families.'" When Moses had finished speaking, all the people bowed down to the ground and worshiped. 28 So the people of Israel did just as the Lord had commanded through Moses and Aaron.
Matthew Henry's Commentary on Exodus 12:21-28
Commentary on Exodus 12:21-28
(Read Exodus 12:21-28)
That night, when the first-born were to be destroyed, no Israelite must stir out of doors till called to march out of Egypt. Their safety was owing to the blood of sprinkling. If they put themselves from under the protection of that, it was at their peril. They must stay within, to wait for the salvation of the Lord; it is good to do so. In after-times they should carefully teach their children the meaning of this service. It is good for children to ask about the things of God; they that ask for the way will find it. The keeping of this solemnity every year was, 1. To look backward, that they might remember what great things God had done for them and their fathers. Old mercies, to ourselves, or to our fathers, must not be forgotten, that God may be praised, and our faith in him encouraged. 2. It was designed to look forward, as an earnest of the great sacrifice of the Lamb of God in the fulness of time. Christ our passover was sacrificed for us; his death was our life.