Thomas Aquinas, Compendium of Theology

Evidently, therefore, as we see from this discussion, Christ took some of our defects on Himself, not out of necessity, but for a definite purpose, namely, for our salvation. But every potency and every habit or capacity are ordained toward act as their end. Hence capacity to suffer is not enough for satisfaction or merit apart from actual suffering. A person is called good or evil, not because he is able to perform good or evil actions, but because he performs them; praise and blame are duly rendered not for power to act but for acting. To save us, consequently, Christ was not content merely to make our passibility His portion, but He willed actually to suffer that He might satisfy for our sins. He endured for us those sufferings which we deserved to suffer in consequence of the sin of our first parent. Of these the chief is death, to which all other human sufferings are ordered as to their final term. "For the wages of sin is death," as the Apostle says in Romans 6:23.

Accordingly Christ willed to submit to death for our sins so that, in taking on Himself without any fault of His own the punishment charged against us, He might free us from the death to which we had been sentenced, in the way that anyone would be freed from a debt of penalty if another person undertook to pay the penalty for him. Another reason why He wished to die was that His death might be for us not only a remedy of satisfaction but also a sacrament of salvation, so that we, transferred to a spiritual life, might die to our carnal life, in the likeness of His death. This is in accord with I Peter 3:18: "Christ also died once for our sins, the just for the unjust, that He might offer us to God, being put to death indeed in the flesh, but enlivened in the spirit."

Christ also wished to die that His death might be an example of perfect virtue for us. He gave an example of charity, for "greater love than this no man hath, that a man lay down his life for his friends" (John 15:13). The more numerous and grievous are the sufferings a person does not refuse to bear for his friend, the more strikingly his love is shown forth. But of all human ills the most grievous is death, by which human life is snuffed out. Hence no greater proof of love is possible than that a man should expose himself to death for a friend.

By His death Christ also gave an example of fortitude, which does not abandon justice in the face of adversity; refusal to give up the practice of virtue even under fear of death seems to pertain most emphatically to fortitude. Thus the Apostle says in Hebrews 2:14 f., with reference to Christ's passion: "That through death He might destroy him who had the empire of death, that is to say, the devil, and might deliver them who through the fear of death were all their lifetime subject to servitude." In not refusing to die for truth, Christ overcame the fear of dying, which is the reason men for the most part are subject to the slavery of sin.

Further, He gave an example of patience, a virtue that prevents sorrow from overwhelming man in time of adversity; the greater the trials, the more splendidly does the virtue of patience shine forth in them. Therefore an example of perfect patience is afforded in the greatest of evils, which is death, if it is borne without distress of mind. Such tranquility the prophet foretold of Christ: He "shall be dumb as a lamb before his shearer, and He shall not open His mouth" (Isa. 53:7).

Lastly, our Lord gave an example of obedience; for the more difficult are the precepts one obeys, the more praiseworthy is the obedience. But the most difficult of all the objects of obedience is death. Hence, to commend the perfect obedience of Christ, the Apostle says, in Philippians 2:8, that He was obedient to the Father even unto death.