Self-same day - בעצם beetsem, in the body of this day, or in the strength of this day; probably they began their march about day-break, called here the body or strength of the day, and in Deuteronomy 16:1, by night - sometime before the sun rose.

And ye shall observe the feast of unleavened bread,.... Which was a distinct feast from the passover feast; for though at that unleavened bread was eaten, it was kept but one night, this seven days; and it is repeated that it might be taken notice of, and the rather, as it was to be observed in all ages as long as the Jewish economy lasted; the reason of which follows:

for in this selfsame day have I brought your armies out of the land of Egypt; which, though not already done, was just on doing, and was certain; and besides, it respects the day when it should come about another year: by their "armies" are meant the tribes of Israel, not so much for their military force, for as yet they were an unarmed people, but for their numbers, which were sufficient to make several considerable armies, and for their order and ease, and their being without any fear of the enemy, in which they marched out of Egypt:

therefore shall ye observe this day in your generations by an ordinance for ever; according to the rules given, with the same exactness, strictness, and constancy, as the first of the passover, and as long as that continued; See Gill on Exodus 12:14.

"Observe the Mazzoth" (i.e., the directions given in Exodus 12:15 and Exodus 12:16 respecting the feast of Mazzoth), "for on this very day I have brought your armies out of the land of Egypt." This was effected in the night of the 14th-15th, or rather at midnight, and therefore in the early morning of the 15th Abib. Because Jehovah had brought Israel out of Egypt on the 15th Abib, therefore Israel was to keep Mazzoth for seven days. Of course it was not merely a commemoration of this event, but the exodus formed the groundwork of the seven days' feast, because it was by this that Israel had been introduced into a new vital element. For this reason the Israelites were to put away all the leaven of their Egyptian nature, the leaven of malice and wickedness (1 Corinthians 5:8), and by eating pure and holy bread, and meeting for the worship of God, to show that they were walking in newness of life. This aspect of the feast will serve to explain the repeated emphasis laid upon the instructions given concerning it, and the repeated threat of extermination against either native or foreigner, in case the law should be disobeyed (Exodus 12:18-20). To eat leavened bread at this feast, would have been a denial of the divine act, by which Israel was introduced into the new life of fellowship with Jehovah. גּר, a stranger, was a non-Israelite who lived for a time, or possibly for his whole life, in the midst of the Israelitish nation, but without being incorporated into it by circumcision. הארץ אזרח, a tree that grows upon the soil in which it was planted; hence indigena, the native of a country. This term was applied to the Israelites, "because they had sprung from Isaac and Jacob, who were born in the land of Canaan, and had received it from God as a permanent settlement" (Clericus). The feast of Mazzoth, the commemoration of Israel's creation as the people of Jehovah (Isaiah 43:15-17), was fixed for seven days, to stamp upon it in the number seven the seal of the covenant relationship. This heptad of days was made holy through the sanctification of the first and last days by the holding of a holy assembly, and the entire suspension of work. The beginning and the end comprehended the whole. In the eating of unleavened bread Israel laboured for meat for the new life (John 6:27), whilst the seal of worship was impressed upon this new life in the holy convocation, and the suspension of labour was the symbol of rest in the Lord.

And ye shall observe the feast of unleavened bread; for in this selfsame day have I brought your armies out of the land of Egypt: therefore shall ye observe this day in your generations by an ordinance for ever.

17. ye shall observe, &c.-The seven days of this feast were to commence the day after the passover. It was a distinct festival following that feast; but although this feast was instituted like the passover before the departure, the observance of it did not take place till after.

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.