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 Obj. 6:  As 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,