Objection 1. It would seem that in Christ there were no virtues. For Christ had the plenitude of grace. Now grace is sufficient for every good act, according to 2 Corinthians 12:9: "My grace is sufficient for thee." Therefore there were no virtues in Christ.
Objection 2. Further, according to the Philosopher (Ethic. vii, 1), virtue is contrasted with a "certain heroic or godlike habit" which is attributed to godlike men. But this belongs chiefly to Christ. Therefore Christ had not virtues, but something higher than virtue.
Objection 3. Further, as was said above (I-II, 65, 1,2), all the virtues are bound together. But it was not becoming for Christ to have all the virtues, as is clear in the case of liberality and magnificence, for these have to do with riches, which Christ spurned, according to Matthew 8:20: "The Son of man hath not where to lay His head." Temperance and continence also regard wicked desires, from which Christ was free. Therefore Christ had not the virtues.
On the contrary, on Psalm 1:2, "But His will is in the law of the Lord," a gloss says: "This refers to Christ, Who is full of all good." But a good quality of the mind is a virtue. Therefore Christ was full of all virtue.
I answer that, As was said above (I-II, 110, 3,4), as grace regards the essence of the soul, so does virtue regard its power. Hence it is necessary that as the powers of the soul flow from its essence, so do the virtues flow from grace. Now the more perfect a principle is, the more it impresses its effects. Hence, since the grace of Christ was most perfect, there flowed from it, in consequence, the virtues which perfect the several powers of the soul for all the soul's acts; and thus Christ had all the virtues.
Reply to Objection 1. Grace suffices a man for all whereby he is ordained to beatitude; nevertheless, it effects some of these by itself--as to make him pleasing to God, and the like; and some others through the medium of the virtues which proceed from grace.
Reply to Objection 2. A heroic or godlike habit only differs from virtue commonly so called by a more perfect mode, inasmuch as one is disposed to good in a higher way than is common to all. Hence it is not hereby proved that Christ had not the virtues, but that He had them most perfectly beyond the common mode. In this sense Plotinus gave to a certain sublime degree of virtue the name of "virtue of the purified soul" (cf. I-II, 61, 5).
Reply to Objection 3. Liberality and magnificence are praiseworthy in regard to riches, inasmuch as anyone does not esteem wealth to the extent of wishing to retain it, so as to forego what ought to be done. But he esteems them least who wholly despises them, and casts them aside for love of perfection. And hence by altogether contemning all riches, Christ showed the highest kind of liberality and magnificence; although He also performed the act of liberality, as far as it became Him, by causing to be distributed to the poor what was given to Himself. Hence, when our Lord said to Judas (John 13:21), "That which thou dost do quickly," the disciples understood our Lord to have ordered him to give something to the poor. But Christ had no evil desires whatever, as will be shown (15, 1,2); yet He was not thereby prevented from having temperance, which is the more perfect in man, as he is without evil desires. Hence, according to the Philosopher (Ethic. vii, 9), the temperate man differs from the continent in this--that the temperate has not the evil desires which the continent suffers. Hence, taking continence in this sense, as the Philosopher takes it, Christ, from the very fact that He had all virtue, had not continence, since it is not a virtue, but something less than virtue.
Source: Summa Theologica (New Advent)