Thus, since they were kinsmen, in order that it should not seem that John would testify concerning Christ because of kinship, the grace of the Spirit organized it such, that John spent all his early years in the wilderness, so that it should not seem that John had declared his testimony out of friendship or some similar reason. But John, as he was instructed of God, thus also announced about Him, wherein also he did say: “and I knew Him not.” From whence didst thou find out? “He, having sent me that sayeth to baptize with water, [is] the One [Who] did tell me” What did He tell thee? “Over Him thou shalt see the Spirit descending, like to a dove, and abiding over Him, that One is baptized by the Holy Spirit” (John 1:32-33). Dost thou see, that the Holy Spirit did not descend as in a first time then coming down upon Him, but in order to point out that preached by His inspiration—as though by a finger—it pointed Him out to all. For this reason He came to baptism.
And there is a second reason, about which He Himself spoke. What exactly is it? When John said, “I have need to be baptized of Thee, and Thou art come to me?” He answered thus: “Stay now, for thus it becometh us to fulfill every righteousness” (Matthew 3:14-15). Dost thou see the meekness of the servant? Dost thou see the humility of the Master? What does He mean, “to fulfill every righteousness?” By righteousness is meant the fulfillment of all the commandments, as is said: “both were righteous, walking faultlessly in the commandments of the Lord” (Luke 1:6). Since fulfilling this righteousness was necessary for all people—but no one of them kept it or fulfilled it—Christ came then and fulfilled this righteousness.
And what righteousness is there, someone will say, in being baptized? Obedience for a prophet was righteous. As Christ was circumcised, offered sacrifice, kept the sabbath and observed the Jewish feasts, so also He added this remaining thing, that He was obedient to having been baptized by a prophet. It was the will of God, then, that all should be baptized—about which John speaks: “He having sent me to baptize with water” (John 1:33); so also Christ: “The publicans and the people do justify God, having been baptized with the baptism of John; the Pharisees and the lawyers reject the counsel of God concerning themselves, not having been baptized by him” (Luke 7:29-30). Thus, if obedience to God constitutes righteousness, and God sent John to baptize the nation, then Christ has also fulfilled this along with all the other commandments.