smearing with blood was to be regarded as an act of expiation, is evident from the simple fact, that a hyssop-bush was used for the purpose (Exo 12:22); for sprinkling with hyssop is never prescribed in the law, except in connection with purification in the sense of expiation (Lev 14:49.; Num 19:18-19). In Egypt the Israelites had no common altar; and for this reason, the houses in which they assembled for the Passover were consecrated as altars, and the persons found in them were thereby removed from the stroke of the destroyer. In this way the smearing of the door-posts and lintel became a sign to Israel of their deliverance from the destroyer. Jehovah made it so by His promise, that He would see the blood, and pass over the houses that were smeared with it. Through faith in this promise, Israel acquired in the sign a firm pledge of its deliverance. The smearing of the doorway was relinquished, after Moses (not Josiah, as Vaihinger supposes, cf. Deu 16:5-6) had transferred the slaying of the lambs to the court of the sanctuary, and the blood had been ordered to be sprinkled upon the altar there.
verses 8-9
With regard to the preparation of the lamb for the meal, the following directions were given: “They shall eat the lamb in that night” (i.e., the night following the 14th), and none of it נא (“underdone” or raw), or בּשׁל (“boiled,” - lit., done, viz., בּמּים מבשּׁל, done in water, i.e., boiled, as בּשׁל does not mean to be boiled, but to become ripe or done, Joe 3:13); “but roasted with fire, even its head on (along with)its thighs and entrails;” i.e., as Rashi correctly explains it, “undivided or whole, so that neither head nor thighs were cut off, and not a bone was broken (Exo 12:46), and the viscera were roasted in the belly along with the entrails,” the latter, of course, being first of all cleansed. On כּרעים and קרב see Lev 1:9. These regulations are all to be regarded from one point of view. The first two, neither underdone nor boiled, were connected with the roasting of the animal whole. As the roasting no doubt took place on a spit, since the Israelites while in Egypt can hardly have possessed such ovens of their own, as are prescribed in the Talmud and are met with in Persia, the lamb would be very likely to be roasted imperfectly, or underdone, especially in the hurry that must have preceded the Exodus (Exo 12:11). By boiling, again, the integrity of the animal would have been destroyed, partly through the fact that it could never have been got into a pot whole, as the Israelites
