The blood shall be to you for a token - It shall be the sign to the destroying angel, that the house on which he sees this blood sprinkled is under the protection of God, and that no person in it is to be injured. See Clarke on Exodus 12:11 (note).

And the blood shall be to you for a token upon the houses where you are,.... The blood of the passover lamb being sprinkled on the two sideposts and upper doorposts of the houses inhabited by the Israelites, or where they were eating the passover; this should be a sign or token to them of the Lord's making good his promises, to them, and so of their safety, and to the destroying angel not to enter therein, but pass by and save them:

and when I see the blood, I will pass over you; for which reason this ordinance now instituted was called the passover, because the Lord, on sight of the blood sprinkled, passed over the houses of the Israelites to those of the Egyptians; or "leaped", as Jarchi says, the word signifies, skipped from one Egyptian house to another, passing by that of the Israelites:

and the plague shall not be upon you, to destroy you, when I smite the land of Egypt, the pestilence with which the firstborn should be destroyed.

To the Israelites, on the other hand, the blood upon the houses in which they were assembled would be a sign and pledge that Jehovah would spare them, and no plague should fall upon them to destroy (cf. Ezekiel 21:31; not "for the destroyer," for there is no article with למשׁחית).

And the blood shall be to you for a token upon the houses where ye are: and when I see the blood, I will pass over you, and the plague shall not be upon you to destroy you, when I smite the land of Egypt.

to destroy...: Heb. for a destruction

12:1-20 The Lord makes all things new to those whom he delivers from the bondage of Satan, and takes to himself to be his people. The time when he does this is to them the beginning of a new life. God appointed that, on the night wherein they were to go out of Egypt, each family should kill a lamb, or that two or three families, if small, should kill one lamb. This lamb was to be eaten in the manner here directed, and the blood to be sprinkled on the door-posts, to mark the houses of the Israelites from those of the Egyptians. The angel of the Lord, when destroying the first-born of the Egyptians, would pass over the houses marked by the blood of the lamb: hence the name of this holy feast or ordinance. The passover was to be kept every year, both as a remembrance of Israel's preservation and deliverance out of Egypt, and as a remarkable type of Christ. Their safety and deliverance were not a reward of their own righteousness, but the gift of mercy. Of this they were reminded, and by this ordinance they were taught, that all blessings came to them through the shedding and sprinkling of blood. Observe, 1. The paschal lamb was typical. Christ is our passover, 1Co 5:7. Christ is the Lamb of God, Joh 1:29; often in the Revelation he is called the Lamb. It was to be in its prime; Christ offered up himself in the midst of his days, not when a babe at Bethlehem. It was to be without blemish; the Lord Jesus was a Lamb without spot: the judge who condemned Christ declared him innocent. It was to be set apart four days before, denoting the marking out of the Lord Jesus to be a Saviour, both in the purpose and in the promise. It was to be slain, and roasted with fire, denoting the painful sufferings of the Lord Jesus, even unto death, the death of the cross. The wrath of God is as fire, and Christ was made a curse for us. Not a bone of it must be broken, which was fulfilled in Christ, Joh 19:33, denoting the unbroken strength of the Lord Jesus. 2. The sprinkling of the blood was typical. The blood of the lamb must be sprinkled, denoting the applying of the merits of Christ's death to our souls; we must receive the atonement, Ro 5:11. Faith is the bunch of hyssop, by which we apply the promises, and the benefits of the blood of Christ laid up in them, to ourselves. It was to be sprinkled on the door-posts, denoting the open profession we are to make of faith in Christ. It was not to be sprinkled upon the threshold; which cautions us to take heed of trampling under foot the blood of the covenant. It is precious blood, and must be precious to us. The blood, thus sprinkled, was a means of preserving the Israelites from the destroying angel, who had nothing to do where the blood was. The blood of Christ is the believer's protection from the wrath of God, the curse of the law, and the damnation of hell, Ro 8:1. 3. The solemn eating of the lamb was typical of our gospel duty to Christ. The paschal lamb was not to be looked upon only, but to be fed upon. So we must by faith make Christ our own; and we must receive spiritual strength and nourishment from him, as from our food, see Joh 6:53,55. It was all to be eaten; those who by faith feed upon Christ, must feed upon a whole Christ; they must take Christ and his yoke, Christ and his cross, as well as Christ and his crown. It was to be eaten at once, not put by till morning. To-day Christ is offered, and is to be accepted while it is called to-day, before we sleep the sleep of death. It was to be eaten with bitter herbs, in remembrance of the bitterness of their bondage in Egypt; we must feed upon Christ with sorrow and brokenness of heart, in remembrance of sin. Christ will be sweet to us, if sin be bitter. It was to be eaten standing, with their staves in their hands, as being ready to depart. When we feed upon Christ by faith, we must forsake the rule and the dominion of sin; sit loose to the world, and every thing in it; forsake all for Christ, and reckon it no bad bargain, Heb 13:13,14. 4. The feast of unleavened bread was typical of the Christian life, 1Co 5:7,8. Having received Christ Jesus the Lord, we must continually delight ourselves in Christ Jesus. No manner of work must be done, that is, no care admitted and indulged, which does not agree with, or would lessen this holy joy. The Jews were very strict as to the passover, so that no leaven should be found in their houses. It must be a feast kept in charity, without the leaven of malice; and in sincerity, without the leaven of hypocrisy. It was by an ordinance for ever; so long as we live we must continue feeding upon Christ, rejoicing in him always, with thankful mention of the great things he has done for us.