Reply Obj. 3: Christ was set before men as an example to all. Wherefore it behooved that to be shown forth in Him, which is becoming to all according to the common law—namely, that He should teach after reaching the perfect age. But, as Gregory Nazianzen says (Orat. xxxix), that which seldom occurs is not the law of the Church; as "neither does one swallow make the spring." For by special dispensation, in accordance with the ruling of Divine wisdom, it has been granted to some, contrary to the common law, to exercise the functions of governing or teaching, such as Solomon, Daniel, and Jeremias.
Reply Obj. 4: It was not fitting that Christ should be baptized by John either before or after all others. Because, as Chrysostom says (Hom. iv in Matth. [*From the supposititious Opus Imperfectum]), for this was Christ baptized, "that He might confirm the preaching and the baptism of John, and that John might bear witness to Him." Now, men would not have had faith in John's testimony except after many had been baptized by him. Consequently it was not fitting that John should baptize Him before baptizing anyone else. In like manner, neither was it fitting that he should baptize Him last. For as he (Chrysostom) says in the same passage: "As the light of the sun does not wait for the setting of the morning star, but comes forth while the latter is still above the horizon, and by its brilliance dims its shining: so Christ did not wait till John had run his course, but appeared while he was yet teaching and baptizing." _______________________
FOURTH ARTICLE [III, Q. 39, Art. 4]
Whether Christ Should Have Been Baptized in the Jordan?
Objection 1: It would seem that Christ should not have been baptized in the Jordan. For the reality should correspond to the figure. But baptism was prefigured in the crossing of the Red Sea, where the Egyptians were drowned, just as our sins are blotted out in baptism. Therefore it seems that Christ should rather have been baptized in the sea than in the river Jordan.
Obj. 2: Further, "Jordan" is interpreted a "going down." But by baptism a man goes up rather than down: wherefore it is written (Matt. 3:16) that "Jesus being baptized, forthwith came up [Douay: 'out'] from the water." Therefore it seems unfitting that Christ should be baptized in the Jordan.
Obj. 3: Further, while the children of Israel were crossing, the waters of the Jordan "were turned back," as it is related Jos. 4, and as it is written Ps. 113:3, 5. But those who are baptized go forward, not back. Therefore it was not fitting that Christ should be baptized in the Jordan.
On the contrary, It is written (Mk. 1:9) that "Jesus was baptized by John in the Jordan."
I answer that, It was through the river Jordan that the children of Israel entered into the land of promise. Now, this is the prerogative of Christ's baptism over all other baptisms: that it is the entrance to the kingdom of God, which is signified by the land of promise; wherefore it is said (John 3:5): "Unless a man be born again of water and the Holy Ghost, he cannot enter into the kingdom of God." To this also is to be referred the dividing of the water of the Jordan by Elias, who was to be snatched up into heaven in a fiery chariot, as it is related 4 Kings 2: because, to wit, the approach to heaven is laid open by the fire of the Holy Ghost, to those who pass through the waters of baptism. Therefore it was fitting that Christ should be baptized in the Jordan.
Reply Obj. 1: The crossing of the Red Sea foreshadowed baptism in this—that baptism washes away sin: whereas the crossing of the Jordan foreshadows it in this—that it opens the gate to the heavenly kingdom: and this is the principal effect of baptism, and accomplished through Christ alone. And therefore it was fitting that Christ should be baptized in the Jordan rather than in the sea.