Alcuin
Catena Aurea · Johannesevangelium 5
If I bear witness of myself, my witness is not true. There is another that beareth witness of me; and I know that the witness which he witnesseth of me is true. Ye sent unto John, and he bare witness unto the truth. But I receive not testimony from man: but these things I say, that ye might be saved. He was a burning and a shining light: and ye were willing for a season to rejoice in his light. But I have greater witness than that of John: for the works which the Father hath given me to finish, the same works that I do, bear witness of me, that the Father hath sent me. And the Father himself, which hath sent me, hath borne witness of me. Ye have neither heard his voice at any time, nor seen his shape. And ye have not his word abiding in you: for whom he hath sent, him ye believe not. Search the Scriptures; for in them ye think ye have eternal life: and they are they which testify of me. And ye will not come to me, that ye might have life.
Or thus; Christ, being both God and man, He shews the proper existence of both, by sometimes speaking according to the nature he took from man, sometimes according to the majesty of the Godhead. If I bear witness of Myself, My witness is not true: this is to be understood of His humanity; the sense being, If I, a man, bear witness of Myself, i. e. without God, My witness is not true: and then follows, There is another that beareth witness of Me. The Father bore witness of Christ, by the voice which was heard at the baptism, and at the transfiguration on the mount. And I know that His witness is true; because He is the God of truth. How then can His witness be otherwise than true?