Objection 1. It would seem that it pertains to Christ to pray according to His sensuality. For it is written (Psalm 83:3) in the person of Christ: "My heart and My flesh have rejoiced in the Living God." Now sensuality is called the appetite of the flesh. Hence Christ's sensuality could ascend to the Living God by rejoicing; and with equal reason by praying.
Objection 2. Further, prayer would seem to pertain to that which desires what is besought. Now Christ besought something that His sensuality desired when He said (Matthew 26:39): "Let this chalice pass from Me." Therefore Christ's sensuality prayed.
Objection 3. Further, it is a greater thing to be united to God in person than to mount to Him in prayer. But the sensuality was assumed by God to the unity of Person, even as every other part of human nature. Much more, therefore, could it mount to God by prayer.
On the contrary, It is written (Philippians 2:7) that the Son of God in the nature that He assumed was "made in the likeness of men." But the rest of men do not pray with their sensuality. Therefore, neither did Christ pray according to His sensuality.
I answer that, To pray according to sensuality may be understood in two ways. First as if prayer itself were an act of the sensuality; and in this sense Christ did not pray with His sensuality, since His sensuality was of the same nature and species in Christ as in us. Now in us the sensuality cannot pray for two reasons; first because the movement of the sensuality cannot transcend sensible things, and, consequently, it cannot mount to God, which is required for prayer; secondly, because prayer implies a certain ordering inasmuch as we desire something to be fulfilled by God; and this is the work of reason alone. Hence prayer is an act of the reason, as was said in the II-II, 83, 1.
Secondly, we may be said to pray according to the sensuality when our prayer lays before God what is in our appetite of sensuality; and in this sense Christ prayed with His sensuality inasmuch as His prayer expressed the desire of His sensuality, as if it were the advocate of the sensuality--and this, that He might teach us three things. First, to show that He had taken a true human nature, with all its natural affections: secondly, to show that a man may wish with his natural desire what God does not wish: thirdly, to show that man should subject his own will to the Divine will. Hence Augustine says in the Enchiridion (Serm. 1 in Ps. 32): "Christ acting as a man, shows the proper will of a man when He says 'Let this chalice pass from Me'; for this was the human will desiring something proper to itself and, so to say, private. But because He wishes man to be righteous and to be directed to God, He adds: 'Nevertheless not as I will but as Thou wilt,' as if to say, 'See thyself in Me, for thou canst desire something proper to thee, even though God wishes something else.'"
Reply to Objection 1. The flesh rejoices in the Living God, not by the act of the flesh mounting to God, but by the outpouring of the heart into the flesh, inasmuch as the sensitive appetite follows the movement of the rational appetite.
Reply to Objection 2. Although the sensuality wished what the reason besought, it did not belong to the sensuality to seek this by praying, but to the reason, as stated above.
Reply to Objection 3. The union in person is according to the personal being, which pertains to every part of the human nature; but the uplifting of prayer is by an act which pertains only to the reason, as stated above. Hence there is no parity.
Source: Summa Theologica (New Advent)