John Calvin on John 3:28

28. You are witnesses to me. John expostulates with his disciples that they did not give credit to his statements. He had often warned them that he was not the Christ; and, therefore, it only remained that he should be a servant and subject to the Son of God along with others. And this passage is worthy of notice; for, by affirming that he is not the Christ, he reserves nothing for himself but to be subject to the head, and to serve in the Church as one of the rest, and not to be so highly exalted as to obscure the honor of the Head. He says that he was sent before, to prepare the way for Christ, as kings are wont to have heralds or forerunners.

John 3:29-34

29. He who hath the bride is the bridegroom; but the friend of the bridegroom, who standeth, and heareth him, rejoiceth exceedingly on account of the bridegroom’s voice. This my joy, therefore, is fulfilled. 30. He must increase, but I must decrease. 31. He who cometh from above is above all; he who is from the earth is of the earth, and speaketh “Et parle de la terre, ou, comme issu de terre;” — “and speaketh of the earthy or, as having proceeded from the earth.” of the earth: he who cometh from heaven is above all. 32. And what he hath seen and heard, this he testifieth, and no man receiveth his testimony. 33. But he who receiveth his testimony hath sealed that God is true. 34. For he whom God hath sent speaketh the words of God, for God giveth not the Spirit by measure.