Summa Theologica I-II, q. 102: Of the Causes of the Ceremonial Precepts
iii, 8,9,10), the four elements are indicated here: for "cedar-wood" was added to the fire, to signify the earth, on account of its earthiness; "hyssop," to signify the air, on account of its smell; "scarlet twice dyed," to signify water, for the same reason as purple, on account of the dyes which are taken out of the water: thus denoting the fact that this sacrifice was offered to the Creator of the four elements. And since this sacrifice was offered for the sin of idolatry, both "he that burned her," and "he that gathered up the ashes," and "he that sprinkled the water" in which the ashes were placed, were deemed unclean in detestation of that sin, in order to show that whatever was in any way connected with idolatry should be cast aside as being unclean. From this uncleanness they were purified by the mere washing of their clothes; nor did they need to be sprinkled with the water on account of this kind of uncleanness, because otherwise the process would have been unending, since he that sprinkled the water became unclean, so that if he were to sprinkle himself he would remain unclean; and if another were to sprinkle him, that one would have become unclean, and in like manner, whoever might sprinkle him, and so on indefinitely.
The figurative reason of this sacrifice was that the red cow signified Christ in respect of His assumed weakness, denoted by the female sex; while the color of the cow designated the blood of His Passion. And the "red cow was of full age," because all Christ's works are perfect, "in which there" was "no blemish"; "and which" had "not carried the yoke," because Christ was innocent, nor did He carry the yoke of sin. It was commanded to be taken to Moses, because they blamed Him for transgressing the law of Moses by breaking the Sabbath. And it was commanded to be delivered "to Eleazar the priest," because Christ was delivered into the hands of the priests to be slain. It was immolated "without the camp," because Christ "suffered outside the gate" (Heb. 13:12). And the priest dipped "his finger in her blood," because the mystery of Christ's Passion should be considered and imitated.
It was sprinkled "over against. . . the tabernacle," which denotes the synagogue, to signify either the condemnation of the unbelieving Jews, or the purification of believers; and this "seven times," in token either of the seven gifts of the Holy Ghost, or of the seven days wherein all time is comprised. Again, all things that pertain to the Incarnation of Christ should be burnt with fire, i.e. they should be understood spiritually; for the "skin" and "flesh" signified Christ's outward works; the "blood" denoted the subtle inward force which quickened His external deeds; the "dung" betokened His weariness, His thirst, and all such like things pertaining to His weakness. Three things were added, viz. "cedar-wood," which denotes the height of hope or contemplation; "hyssop," in token of humility or faith; "scarlet twice dyed," which denotes twofold charity; for it is by these three that we should cling to Christ suffering. The ashes of this burning were gathered by "a man that is clean," because the relics of the Passion came into the possession of the Gentiles, who were not guilty of Christ's death. The ashes were put into water for the purpose of expiation, because Baptism receives from Christ's Passion the power of washing away sins. The priest who immolated and burned the cow, and he who burned, and he who gathered together the ashes, were unclean, as also he that sprinkled the water: either because the Jews became unclean through putting Christ to death, whereby our sins are expiated; and this, until the evening, i.e. until the end of the world, when the remnants of Israel will be converted; or else because they who handle sacred things with a view to the cleansing of others contract certain uncleannesses, as Gregory says (Pastor. ii, 5); and this until the evening, i.e. until the end of this life.
Reply to Objection 6As stated above (ad 5), an uncleanness which was caused by corruption either of mind or of body was expiated by sin-offerings. Now special sacrifices were wont to be offered for the sins of individuals: but since some were neglectful about expiating such sins and uncleannesses; or, through ignorance, failed to offer this expiation; it was laid down that once a year, on the tenth day of the seventh month, a sacrifice of expiation should be offered for the whole people. And because, as the Apostle says (Heb. 7:28), "the Law maketh men priests, who have infirmity," it behooved the priest first of all to offer a calf for his own sins, in memory of Aaron's sin in fashioning the molten calf; and besides, to offer a ram for a holocaust, which signified that the priestly sovereignty denoted by the ram, who is the head of the flock, was to be ordained to the glory of God. Then he offered two he-goats for the people: one of which was offered in expiation of the sins of the multitude. For the he-goat is an evil-smelling animal; and from its skin clothes are made having a pungent odor; to signify the stench, uncleanness and the sting of sin. After this he-goat had been immolated, its blood was taken, together with the blood of the calf, into the Holy of Holies, and the entire sanctuary was sprinkled with it; to signify that the tabernacle was cleansed from the uncleanness of the children of Israel. But the corpses of the he-goat and calf which had been offered up for sin had to be burnt, to denote the destruction of sins. They were not, however, burnt on the altar: since none but holocausts were burnt thereon; but it was prescribed that they should be burnt without the camp, in detestation of sin: for this was done whenever sacrifice was offered for a grievous sin, or for the multitude of sins. The other goat was let loose into the wilderness: not indeed to offer it to the demons, whom the Gentiles worshipped in desert places, because it was unlawful to offer aught to them; but in order to point out the effect of the sacrifice which had been offered up. Hence the priest put his hand on its head, while confessing the sins of the children of Israel: as though that goat were to carry them away into the wilderness, where it would be devoured by wild beasts, because it bore the punishment of the people's sins.
And it was said to bear the sins of the people, either because the forgiveness of the people's sins was signified by its being let loose, or because on its head written lists of sins were fastened.
The figurative reason of these things was that Christ was foreshadowed both by the calf, on account of His power; and by the ram, because He is the Head of the faithful; and by the he-goat, on account of "the likeness of sinful flesh" (Rom. 8:3). Moreover, Christ was sacrificed for the sins of both priests and people: since both those of high and those of low degree are cleansed from sin by His Passion. The blood of the calf and of the goat was brought into the Holies by the priest, because the entrance to the kingdom of heaven was opened to us by the blood of Christ's Passion. Their bodies were burnt without the camp, because "Christ suffered without the gate," as the Apostle declares (Heb. 13:12). The scape-goat may denote either Christ's Godhead Which went away into solitude when the Man Christ suffered, not by going to another place, but by restraining His power: or it may signify the base concupiscence which we ought to cast away from ourselves, while we offer up to Our Lord acts of virtue.