Thomas Aquinas

“ Thirdly, human nature is especially subject to God through its proper act, inasmuch as by its own will it obeys His command. This triple subjection to God Christ professes of Himself. The first (Mat. 19:17) : "Why askest thou Me concerning good? One is good, God." And on this Jerome remarks: "He who had called Him a good master, and had not confessed Him to be God or the Son of God, learns that no man, however holy, is good in comparison with God." And hereby He gave us to understand that He Himself, in His human nature, did not attain to the height of Divine goodness. ”

“ Therefore the Son is greater than Himself in human nature.
Further, Christ in His human nature is the servant of God the Father, according to Jn. 20:17: "I ascend to My Father and to your Father to My God and your God." Now whoever is the servant of the Father is the servant of the Son; otherwise not everything that belongs to the Father would belong to the Son. Therefore Christ is His own servant and is subject to Himself.
I answer that, As was said above (A [1] , ad 2) , to be master or servant is attributed to a person or hypostasis according to a nature. ”

“ If anyone say that the Word begotten of God the Father is the God or Lord of Christ, and does not rather confess the same to be at once God and man as the Word made flesh, according to the Scriptures, let him be anathema. ”

“ Secondly, it may be understood of the diversity of natures in the one person or hypostasis. And thus we may say that in one of them, in which He agrees with the Father, He presides and rules together with the Father; and in the other nature, in which He agrees with us, He is subject and serves, and in this sense Augustine says that "the Son is less than Himself." ”