Reply Obj. 4: God "made Christ sin"—not, indeed, in such sort that He had sin, but that He made Him a sacrifice for sin: even as it is written (Osee 4:8): "They shall eat the sins of My people"—they, i.e. the priests, who by the law ate the sacrifices offered for sin. And in that way it is written (Isa. 53:6) that "the Lord hath laid on Him the iniquity of us all" (i.e. He gave Him up to be a victim for the sins of all men); or "He made Him sin" (i.e. made Him to have "the likeness of sinful flesh"), as is written (Rom. 8:3), and this on account of the passible and mortal body He assumed.
Reply Obj. 5: A penitent can give a praiseworthy example, not by having sinned, but by freely bearing the punishment of sin. And hence Christ set the highest example to penitents, since He willingly bore the punishment, not of His own sin, but of the sins of others. _______________________
SECOND ARTICLE [III, Q. 15, Art. 2]
Whether There Was the Fomes of Sin in Christ?
Objection 1: It would seem that in Christ there was the fomes of sin. For the fomes of sin, and the passibility and mortality of the body spring from the same principle, to wit, from the withdrawal of original justice, whereby the inferior powers of the soul were subject to the reason, and the body to the soul. Now passibility and mortality of body were in Christ. Therefore there was also the fomes of sin.
Obj. 2: Further, as Damascene says (De Fide Orth. iii, 19), "it was by consent of the Divine will that the flesh of Christ was allowed to suffer and do what belonged to it." But it is proper to the flesh to lust after its pleasures. Now since the fomes of sin is nothing more than concupiscence, as the gloss says on Rom. 7:8, it seems that in Christ there was the fomes of sin.
Obj. 3: Further, it is by reason of the fomes of sin that "the flesh lusteth against the spirit," as is written (Gal. 5:17). But the spirit is shown to be so much the stronger and worthier to be crowned according as the more completely it overcomes its enemy—to wit, the concupiscence of the flesh, according to 2 Tim. 2:5, he "is not crowned except he strive lawfully." Now Christ had a most valiant and conquering spirit, and one most worthy of a crown, according to Apoc. 6:2: "There was a crown given Him, and He went forth conquering that He might conquer." Therefore it would especially seem that the fomes of sin ought to have been in Christ.
On the contrary, It is written (Matt. 1:20): "That which is conceived in her is of the Holy Ghost." Now the Holy Ghost drives out sin and the inclination to sin, which is implied in the word fomes. Therefore in Christ there ought not to have been the fomes of sin.
I answer that, As was said above (Q. 7, AA. 2, 9), Christ had grace and all the virtues most perfectly. Now moral virtues, which are in the irrational part of the soul, make it subject to reason, and so much the more as the virtue is more perfect; thus, temperance controls the concupiscible appetite, fortitude and meekness the irascible appetite, as was said in the Second Part (I-II, Q. 56, A. 4). But there belongs to the very nature of the fomes of sin an inclination of the sensual appetite to what is contrary to reason. And hence it is plain that the more perfect the virtues are in any man, the weaker the fomes of sin becomes in him. Hence, since in Christ the virtues were in their highest degree, the fomes of sin was nowise in Him; inasmuch, also, as this defect cannot be ordained to satisfaction, but rather inclined to what is contrary to satisfaction.
Reply Obj. 1: The inferior powers pertaining to the sensitive appetite have a natural capacity to be obedient to reason; but not the bodily powers, nor those of the bodily humors, nor those of the vegetative soul, as is made plain Ethic. i, 13. And hence perfection of virtue, which is in accordance with right reason, does not exclude passibility of body; yet it excludes the fomes of sin, the nature of which consists in the resistance of the sensitive appetite to reason.