A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
exo 12:1THE PASSOVER INSTITUTED. (Exo 12:1-10)
the Lord spake unto Moses--rather, "had spoken unto Moses and Aaron"; for it is evident that the communication here described must have been made to them on or before the tenth of the month.
exo 12:2this month shall be unto you the beginning of months--the first not only in order but in estimation. It had formerly been the seventh according to the reckoning of the civil year, which began in September, and continued unchanged, but it was thenceforth to stand first in the national religious year which began in March, April.
exo 12:3Speak ye unto all the congregation of Israel--The recent events had prepared the Israelitish people for a crisis in their affairs, and they seem to have yielded implicit obedience at this time to Moses. It is observable that, amid all the hurry and bustle of such a departure, their serious attention was to be given to a solemn act of religion.
a lamb for an house--a kid might be taken (Exo 12:5). The service was to be a domestic one, for the deliverance was to be from an evil threatened to every house in Egypt.
exo 12:4if the household be too little for the lamb, &c.--It appears from JOSEPHUS that ten persons were required to make up the proper paschal communion.
every man according to his eating--It is said that the quantity eaten of the paschal lamb, by each individual, was about the size of an olive.
exo 12:5lamb . . . without blemish--The smallest deformity or defect made a lamb unfit for sacrifice--a type of Christ (Heb 7:26; Pe1 1:19).
a male of the first year--Christ in the prime of life.
exo 12:6keep it up until the fourteenth day, &c.--Being selected from the rest of the flock, it was to be separated four days before sacrifice; and for the same length of time was Christ under examination and His spotless innocence declared before the world.
kill it in the evening--that is, the interval between the sun's beginning to decline, and sunset, corresponding to our three o'clock in the afternoon.
exo 12:7take of the blood, and strike it on the two side-posts, &c.--as a sign of safety to those within. The posts must be considered of tents, in which the Israelites generally lived, though some might be in houses. Though the Israelites were sinners as well as the Egyptians, God was pleased to accept the substitution of a lamb--the blood of which, being seen sprinkled on the doorposts, procured them mercy. It was to be on the sideposts and upper doorposts, where it might be looked to, not on the threshold, where it might be trodden under foot. This was an emblem of the blood of sprinkling (Heb 12:24; Heb 10:29).
exo 12:8roast with fire--for the sake of expedition; and this difference was always observed between the cooking of the paschal lamb and the other offerings (Ch2 35:13).
unleavened bread--also for the sake of despatch (Deu 16:3), but as a kind of corruption (Luk 12:1) there seems to have been a typical meaning under it (Co1 5:8).
bitter herbs--literally, "bitters"--to remind the Israelites of their affliction in Egypt, and morally of the trials to which God's people are subject on account of sin.
exo 12:9Eat not of it raw--that is, with any blood remaining; a caveat against conformity to idolatrous practices. It was to be roasted whole, not a bone to be broken, and this pointed to Christ (Joh 19:36).
exo 12:10let nothing of it remain until the morning--which might be applied in a superstitious manner, or allowed to putrefy, which in a hot climate would speedily have ensued; and which was not becoming in what had been offered to God.
exo 12:11THE RITE OF THE PASSOVER. (Exo 12:11-14)
thus shall ye eat it; with your loins girded, your shoes on your feet--as prepared for a journey. The first was done by the skirts of the loose outer cloth being drawn up and fastened in the girdle, so as to leave the leg and knee free for motion. As to the other, the Orientals never wear shoes indoors, and the ancient Egyptians, as appears from the monuments, did not usually wear either shoes or sandals. These injunctions seem to have applied chiefly to the first celebration of the rite.
it is the Lord's passover--called by this name from the blood-marked dwellings of the Israelites being passed over figuratively by the destroying angel.
exo 12:12smite . . . gods of Egypt--perhaps used here for princes and grandees. But, according to Jewish tradition, the idols of Egypt were all on that night broken in pieces (see Num 33:4; Isa 19:1).
exo 12:14for a memorial, &c.--The close analogy traceable in all points between the Jewish and Christian passovers is seen also in the circumstance that both festivals were instituted before the events they were to commemorate had transpired.
exo 12:15UNLEAVENED BREAD. (Exo. 12:15-51)
Seven days shall ye eat unleavened bread, &c.--This was to commemorate another circumstance in the departure of the Israelites, who were urged to leave so hurriedly that their dough was unleavened (Exo 12:39), and they had to eat unleavened cakes (Deu 16:3). The greatest care was always taken by the Jews to free their houses from leaven--the owner searching every corner of his dwelling with a lighted candle. A figurative allusion to this is made (Co1 5:7). The exclusion of leaven for seven days would not be attended with inconvenience in the East, where the usual leaven is dough kept till it becomes sour, and it is kept from one day to another for the purpose of preserving leaven in readiness. Thus even were there none in all the country, it could be got within twenty-four hours [HARMER].
that soul shall be cut off--excommunicated from the community and privileges of the chosen people.
exo 12:16there shall be an holy convocation--literally, calling of the people, which was done by sound of trumpets (Num 10:2), a sacred assembly--for these days were to be regarded as Sabbaths--excepting only that meat might be cooked on them (Exo 16:23).
exo 12:17ye 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.
exo 12:19stranger--No foreigner could partake of the passover, unless circumcised; the "stranger" specified as admissible to the privilege must, therefore, be considered a Gentile proselyte.
exo 12:21Then Moses called for all the elders of Israel, &c.--Here are given special directions for the observance.
exo 12:22hyssop--a small red moss [HASSELQUIST]; the caper-plant [ROYLE]. It was used in the sprinkling, being well adapted for such purposes, as it grows in bushes--putting out plenty of suckers from a single root. And it is remarkable that it was ordained in the arrangements of an all-wise Providence that the Roman soldiers should undesignedly, on their part, make use of this symbolical plant to Christ when, as our Passover, He was sacrificed for us [Joh 19:29].
none . . . shall go out at the door of his house until the morning--This regulation was peculiar to the first celebration, and intended, as some think, to prevent any suspicion attaching to them of being agents in the impending destruction of the Egyptians; there is an allusion to it (Isa 26:20).
exo 12:26when your children shall say, . . . What mean ye by this service--Independently of some observances which were not afterwards repeated, the usages practised at this yearly commemorative feast were so peculiar that the curiosity of the young would be stimulated, and thus parents had an excellent opportunity, which they were enjoined to embrace, for instructing each rising generation in the origin and leading facts of the national faith.
exo 12:27the people bowed the head, and worshipped--All the preceding directions were communicated through the elders, and the Israelites, being deeply solemnized by the influence of past and prospective events, gave prompt and faithful obedience.
exo 12:29at midnight the Lord smote all the first-born in the land of Egypt--At the moment when the Israelites were observing the newly instituted feast in the singular manner described, the threatened calamity overtook the Egyptians. It is more easy to imagine than describe the confusion and terror of that people suddenly roused from sleep and enveloped in darkness--none could assist their neighbors when the groans of the dying and the wild shrieks of mourners were heard everywhere around. The hope of every family was destroyed at a stroke. This judgment, terrible though it was, evinced the equity of divine retribution. For eighty years the Egyptians had caused the male children of the Israelites to be cast into the river [Exo 1:16], and now all their own first-born fell under the stroke of the destroying angel. They were made, in the justice of God, to feel something of what they had made His people feel. Many a time have the hands of sinners made the snares in which they have themselves been entangled, and fallen into the pit which they have dug for the righteous [Pro 28:10]. "Verily there is a God that judgeth in the earth" [Psa 58:11].
exo 12:30there was not a house where there was not one dead--Perhaps this statement is not to be taken absolutely. The Scriptures frequently use the words "all," "none," in a comparative sense--and so in this case. There would be many a house in which there would be no child, and many in which the first-born might be already dead. What is to be understood is, that almost every house in Egypt had a death in it.
exo 12:31called for Moses and Aaron--a striking fulfilment of the words of Moses (Exo 11:8), and showing that they were spoken under divine suggestion.
exo 12:32also take your flocks, &c.--All the terms the king had formerly insisted on were now departed from; his pride had been effectually humbled. Appalling judgments in such rapid succession showed plainly that the hand of God was against him. His own family bereavement had so crushed him to the earth that he not only showed impatience to rid his kingdom of such formidable neighbors, but even begged an interest in their prayers.
exo 12:34people took . . . their kneading-troughs--Having lived so long in Egypt, they must have been in the habit of using the utensils common in that country. The Egyptian kneading-trough was a bowl of wicker or rush work, and it admitted of being hastily wrapped up with the dough in it and slung over the shoulder in their hykes or loose upper garments.
exo 12:35children of Israel borrowed of the Egyptians jewels of silver--When the Orientals go to their sacred festivals, they always put on their best jewels. The Israelites themselves thought they were only going three days' journey to hold a feast unto the Lord, and in these circumstances it would be easy for them to borrow what was necessary for a sacred festival. But borrow conveys a wrong meaning. The word rendered borrow signifies properly to ask, demand, require. The Israelites had been kept in great poverty, having received little or no wages. They now insisted on full remuneration for all their labor, and it was paid in light and valuable articles adapted for convenient carriage.
exo 12:36the Lord gave the people favour in the sight of the Egyptians--Such a dread of them was inspired into the universal minds of the Egyptians, that whatever they asked was readily given.
spoiled the Egyptians--The accumulated earnings of many years being paid them at this moment, the Israelites were suddenly enriched, according to the promise made to Abraham (Gen 15:14), and they left the country like a victorious army laden with spoil (Psa 105:37; Eze 39:10).
exo 12:37The children of Israel journeyed from Rameses--now generally identified with the ancient Heroopolis, and fixed at the modern Abu-Keisheid. This position agrees with the statement that the scene of the miraculous judgments against Pharaoh was "in the field of Zoan" [Psa 78:12, Psa 78:43]. And it is probable that, in expectation of their departure, which the king on one pretext or another delayed, the Israelites had been assembled there as a general rendezvous. In journeying from Rameses to Palestine, there was a choice of two routes--the one along the shores of the Mediterranean to El-Arish, the other more circuitous round the head of the Red Sea and the desert of Sinai. The latter Moses was directed to take (Exo 13:17).
to Succoth--that is, booths, probably nothing more than a place of temporary encampment. The Hebrew word signifies a covering or shelter formed by the boughs of trees; and hence, in memory of this lodgment, the Israelites kept the feast of tabernacles yearly in this manner.
six hundred thousand . . . men--It appears from Num 1:3 that the enumeration is of men above twenty years of age. Assuming, what is now ascertained by statistical tables, that the number of males above that age is as nearly as possible the half of the total number of males, the whole male population of Israel, on this computation, would amount to 1,200,000; and adding an equal number for women and children, the aggregate number of Israelites who left Egypt would be 2,400,000.
exo 12:38a mixed multitude went with them--literally, "a great rabble" (see also Num 11:4; Deu 29:11); slaves, persons in the lowest grades of society, partly natives and partly foreigners, bound close to them as companions in misery, and gladly availing themselves of the opportunity to escape in the crowd. (Compare Zac 8:23).
exo 12:40the sojourning of the children of Israel . . . four hundred and thirty years--The Septuagint renders it thus: "The sojourning of the children and of their fathers, which they sojourned in the land of Canaan and in the land of Egypt." These additions are important, for the period of sojourn in Egypt did not exceed two hundred fifteen years; but if we reckon from the time that Abraham entered Canaan and the promise was made in which the sojourn of his posterity in Egypt was announced, this makes up the time to four hundred thirty years.
exo 12:41even the selfsame day--implying an exact and literal fulfilment of the predicted period.
exo 12:49One law shall be to him that is homeborn, and unto the stranger--This regulation displays the liberal spirit of the Hebrew institutions. Any foreigner might obtain admission to the privileges of the nation on complying with their sacred ordinances. In the Mosaic equally as in the Christian dispensation, privilege and duty were inseparably conjoined.