John 1:31

31.And I knew him not. That his testimony may not be suspected of having been given either from friendship or favor, he anticipates such a doubt, by affirming that he had no other knowledge of Christ than what he had obtained by divine inspiration. The meaning, therefore, amounts to this, that John does not speak at his own suggestion, nor for the favor of man, but by the inspiration of the Spirit and the command of God.

I came baptizing with water; that is, I was called and appointed to this office,that I might manifest him to Israel; which the Evangelist afterwards explains more fully, and confirms, when he introduces John the Baptist, testifying that he had no knowledge of Christ but what he had obtained by oracle; that is, by information or revelation from God. (38) Instead of what we find here, I came to baptize, he there states expressly (verse 33) that he was sent; for it is only the calling of God that makes lawful ministers, because every person who of his own accord, thrusts himself forward, whatever learning or eloquence he may possess, is not entitled to any authority, and the reason is, that he is not authorized by God. Now since it was necessary that John, in order that he might lawfully baptize, should be sent by God, let it be inferred from this, that it is not in the power of any man whatever to institute sacraments, but that this right belongs to God alone, as Christ, on another occasion, in order to prove the baptism of John, asks if it was from heaven, or from men, (Matthew 21:25.)