Summa Theologica I-II, q. 102: Of the Causes of the Ceremonial Precepts
Now of all the gifts which God vouchsafed to mankind after they had fallen away by sin, the chief is that He gave His Son; wherefore it is written (Jn. 3:16): "God so loved the world, as to give His only-begotten Son; that whosoever believeth in Him, may not perish, but may have life everlasting." Consequently the chief sacrifice is that whereby Christ Himself "delivered Himself. . . to God for an odor of sweetness" (Eph. 5:2). And for this reason all the other sacrifices of the Old Law were offered up in order to foreshadow this one individual and paramount sacrifice—the imperfect forecasting the perfect. Hence the Apostle says (Heb. 10:11) that the priest of the Old Law "often" offered "the same sacrifices, which can never take away sins: but" Christ offered "one sacrifice for sins, for ever." And since the reason of the figure is taken from that which the figure represents, therefore the reasons of the figurative sacrifices of the Old Law should be taken from the true sacrifice of Christ.
Reply to Objection 1God did not wish these sacrifices to be offered to Him on account of the things themselves that were offered, as though He stood in need of them: wherefore it is written (Is. 1:11): "I desire not holocausts of rams, and fat of fatlings, and blood of calves and lambs and buckgoats." But, as stated above, He wished them to be offered to Him, in order to prevent idolatry; in order to signify the right ordering of man's mind to God; and in order to represent the mystery of the Redemption of man by Christ.
Reply to Objection 2In all the respects mentioned above (ad 1), there was a suitable reason for these animals, rather than others, being offered in sacrifice to God. First, in order to prevent idolatry. Because idolaters offered all other animals to their gods, or made use of them in their sorceries: while the Egyptians (among whom the people had been dwelling) considered it abominable to slay these animals, wherefore they used not to offer them in sacrifice to their gods. Hence it is written (Ex. 8:26): "We shall sacrifice the abominations of the Egyptians to the Lord our God." For they worshipped the sheep; they reverenced the ram (because demons appeared under the form thereof); while they employed oxen for agriculture, which was reckoned by them as something sacred.
Secondly, this was suitable for the aforesaid right ordering of man's mind to God: and in two ways. First, because it is chiefly by means of these animals that human life is sustained: and moreover they are most clean, and partake of a most clean food: whereas other animals are either wild, and not deputed to ordinary use among men: or, if they be tame, they have unclean food, as pigs and geese: and nothing but what is clean should be offered to God. These birds especially were offered in sacrifice because there were plenty of them in the land of promise. Secondly, because the sacrificing of these animals represented purity of heart. Because as the gloss says on Lev. 1, "We offer a calf, when we overcome the pride of the flesh; a lamb, when we restrain our unreasonable motions; a goat, when we conquer wantonness; a turtledove, when we keep chaste; unleavened bread, when we feast on the unleavened bread of sincerity." And it is evident that the dove denotes charity and simplicity of heart.
Thirdly, it was fitting that these animals should be offered, that they might foreshadow Christ. Because, as the gloss observes, "Christ is offered in the calf, to denote the strength of the cross; in the lamb, to signify His innocence; in the ram, to foreshadow His headship; and in the goat, to signify the likeness of 'sinful flesh'. The turtledove and dove denoted the union of the two natures"; or else the turtledove signified chastity; while the dove was a figure of charity. "The wheat-flour foreshadowed the sprinkling of believers with the water of Baptism."
Reply to Objection 3Fish through living in water are further removed from man than other animals, which, like man, live in the air. Again, fish die as soon as they are taken out of water; hence they could not be offered in the temple like other animals.
Reply to Objection 4Among turtledoves the older ones are better than the young; while with doves the case is the reverse. Wherefore, as Rabbi Moses observes (Doct. Perplex. iii), turtledoves and young doves are commanded to be offered, because nothing should be offered to God but what is best.
Reply to Objection 5The animals which were offered in sacrifice were slain, because it is by being killed that they become useful to man, forasmuch as God gave them to man for food. Wherefore also they were burnt with fire: because it is by being cooked that they are made fit for human consumption. Moreover the slaying of the animals signified the destruction of sins: and also that man deserved death on account of his sins; as though those animals were slain in man's stead, in order to betoken the expiation of sins. Again the slaying of these animals signified the slaying of Christ.
Reply to Objection 6The Law fixed the special manner of slaying the sacrificial animals in order to exclude other ways of killing, whereby idolaters sacrificed animals to idols. Or again, as Rabbi Moses says (Doct. Perplex. iii), "the Law chose that manner of slaying which was least painful to the slain animal." This excluded cruelty on the part of the offerers, and any mangling of the animals slain.
Reply to Objection 7It is because unclean animals are wont to be held in contempt among men, that it was forbidden to offer them in sacrifice to God: and for this reason too they were forbidden (Dt. 23:18) to offer "the hire of a strumpet or the price of a dog in the house of. . . God." For the same reason they did not offer animals before the seventh day, because such were abortive as it were, the flesh being not yet firm on account of its exceeding softness.
Reply to Objection 8There were three kinds of sacrifices. There was one in which the victim was entirely consumed by fire: this was called "a holocaust, i.e. all burnt." For this kind of sacrifice was offered to God specially to show reverence to His majesty, and love of His goodness: and typified the state of perfection as regards the fulfilment of the counsels. Wherefore the whole was burnt up: so that as the whole animal by being dissolved into vapor soared aloft, so it might denote that the whole man, and whatever belongs to him, are subject to the authority of God, and should be offered to Him.
Another sacrifice was the "sin-offering," which was offered to God on account of man's need for the forgiveness of sin: and this typifies the state of penitents in satisfying for sins. It was divided into two parts: for one part was burnt; while the other was granted to the use of the priests to signify that remission of sins is granted by God through the ministry of His priests. When, however, this sacrifice was offered for the sins of the whole people, or specially for the sin of the priest, the whole victim was burnt up. For it was not fitting that the priests should have the use of that which was offered for their own sins, to signify that nothing sinful should remain in them. Moreover, this would not be satisfaction for sin: for if the offering were granted to the use of those for whose sins it was offered, it would seem to be the same as if it had not been offered.