John 1:7

7. οὗτος ἦλθεν εἰς μαρτυρίαν, ἵνα μαρτυρήσῃ περὶ τοῦ φωτός, ἵνα πάντες πιστεύσωσιν δι' αὐτοῦ.

7. He came for a witness, to bear witness of the light, so that through him all men might learn to believe.

7. Hic venit in testimonium ut testimonium perhiberet de lumine, ut omnes crederent per illum.

Blue Letter Bible Reference

John Chrysostom (c.346-407)
Homily 6 on the Gospel of John

“The same came for a witness, to bear witness of that Light.” 

What is this, perhaps one may say, the servant bear witness to his Master? When then you see Him not only witnessed to by His servant, but even coming to him, and with Jews baptized by him, will you not be still more astonished and perplexed? Yet you ought not to be troubled nor confused, but amazed at such unspeakable goodness. Though if any still continue bewildered and confused, He will say to such an one what He said to John, “Suffer it to be so now, for thus it becomes us to fulfill all righteousness” (Matthew 3:15); and, if any be still further troubled, again He will say to him too what he said to the Jews, “But I receive not testimony from man.” (John 5:34) If now he needs not this witness, why was John sent from God? Not as though He required his testimony— this were extremest blasphemy. Why then? John himself informs us, when he says,

“That all men through him might believe.” 

And Christ also, after having said that “I receive not testimony from man” (John 5:34), in order that He may not seem to the foolish to clash with Himself, by declaring at one time “There is another that bears witness of Me and I know that his witness is true” (John 5:32) (for He pointed to John;) and at another, “I receive not testimony from man” (John 5:34); He immediately adds the solution of the doubt, “But these things I say” for your own sake, “that you might be saved.” As though He had said, that “I am God, and the really-Begotten Son of God, and am of that Simple and Blessed Essence, I need none to witness to Me; and even though none would do so, yet am not I by this anything diminished in My Essence; but because I care for the salvation of the many, I have descended to such humility as to commit the witness of Me to a man.” For by reason of the groveling nature and infirmity of the Jews, the faith in Him would in this way be more easily received, and more palatable. As then He clothed Himself with flesh, that he might not, by encountering men with the unveiled Godhead, destroy them all; so He sent forth a man for His herald, that those who heard might at the hearing of a kindred voice approach more readily. For (to prove) that He had no need of that (herald's) testimony, it would have sufficed that He should only have shown Himself who He was in His unveiled Essence, and have confounded them all. But this He did not for the reason I have before mentioned. He would have annihilated all, since none could have endured the encounter of that unapproachable light. Wherefore, as I said, He put on flesh, and entrusted the witness (of Himself) to one of our fellow-servants, since He arranged all for the salvation of men, looking not only to His own honor, but also to what might be readily received by, and be profitable to, His hearers. Which He glanced at when He said, “These things I say” for your sake, “that you might be saved.” (John 5:34) And the Evangelist using the same language as his Master, after saying, “to bear witness of that Light,” adds, “That all men through Him might believe.” All but saying, Think not that the reason why John the Baptist came to bear witness, was that he might add anything to the trustworthiness of his Master. No; (He came,) that by his means beings of his own class might believe. For it is clear from what follows, that he used this expression in his anxiety to remove this suspicion beforehand, since he adds, “He was not that Light.” (John 1:8).