Tertullian, On Baptism 10

We have said what our modest abilities allowed about everything that constitutes the religion of Baptism; now I will move on, as best I can, to its remaining aspect, dealing with certain minor questions. The Baptism announced by John already faced a question posed by the Lord himself to the Pharisees: was that Baptism heavenly, or truly earthly? They could not give a consistent answer, because they did not understand, because they did not believe. We, furthermore, can assess it with only as much understanding as we have faith: that Baptism was indeed divine, but by command, not by power. We read that John was sent by the Lord into this office, yet human in condition. For he exhibited nothing heavenly, but served heavenly things—specifically, he was put in charge of repentance, which lies within human power. Finally, the teachers of the law and the Pharisees, who refused to believe, did not even practice repentance. Now, if repentance is human, then Baptism of the same nature had to be human as well; otherwise it would have granted both the Holy Spirit and the remission of sins, if it were heavenly. But it forgives neither sin nor grants the Spirit—God alone does that. Even the Lord himself, unless he had first ascended to the Father, denied in another way that the Spirit would descend. What the Lord was not yet conferring, a servant certainly could not provide. So much so that later we find in the Acts of the Apostles that those who had John's Baptism had not received the Holy Spirit, whom they did not even know by hearing; therefore it was not heavenly, because it did not exhibit heavenly things. Since the very thing that was heavenly in John, the spirit of prophecy, failed after the transfer of the whole Spirit into the Lord—so much so that he who had predicted, he who had designated the Coming One, afterwards inquired whether he himself had sent him. Therefore, Baptism was administered for repentance, as a candidate for the remission and sanctification in Christ that would follow. For what he preached—a Baptism of repentance for the remission of sins—was announced for a future remission. Indeed, repentance precedes, remission follows, and this is to prepare the way: he who prepares does not himself perfect, but procures perfection for another. He himself professes that his things are not heavenly, but Christ's, saying: 'He who is from the earth speaks from the earth; he who comes from above is above all' (John 3:31). Also, to baptize only in repentance; soon to come is the one who will baptize in Spirit and fire. Clearly, because the true and stable faith of water by which one is baptized for salvation; but the simulated and weak faith is baptized in fire for judgment.