The baptism of Christ was
I. The proclamation of His human relationship to man, and of His human relationship to God. His development had reached its height. He was clearly conscious of His Divine nature. He was clearly conscious of His complete union with our nature. But His Divine nature, so far as its omnipotence, omnipresence, and omniscience so far as all that could separate Him from sharing perfectly in our humanity was concerned, was to remain uncommunicated as yet to His natural, growing humanity; while the perfect holiness, the perfect spiritual character of God, were to be exhibited unmarred, through the medium of His humanity. Hence His baptism was the formalized proclamation of His sinless human nature. He declared by that act that, as man, He submitted Himself to the will of His Father, as shown in the mission of the Baptist.
II. John's baptism prepared those who underwent it for admission into the kingdom which was at hand; it consecrated them to the new work of the new kingdom. In their case two conditions had to be fulfilled repentance and a sense of sin. But these conditions were impossible to Christ. He had no sense of sin. He needed no repentance. The import of the rite was then different in His case. It consecrated Him King of the theocratic kingdom, and proclaimed to all men that His organization of that kingdom had begun. Thus, while the historical meaning of the rite varied with the subjects to whom it was administered, there was an element of preparation in it which was common to both. It consecrated the people to be members of the theocratic kingdom; it consecrated Christ to be the theocratic King; but it marked for both the commencement of a new course of life, in which the subjects of the Kingdom were to receive pardon and life; in which the King was to accomplish the work of salvation, and to bestow life upon His followers.
S. A. Brooke, Sermons,1st series, p. 236.
References: Matthew 3:13-17. Homiletic Magazine,vol. x., pp. 65, 224; Parker, Inner Life of Christ,vol. i., p. 90.