There is another that beareth witness of me
Meaning not his Father, who is another, and a distinct person, from him, as the Spirit is another comforter; and both distinct testifiers from him, as well as of him. This is indeed the sense of some interpreters; but the Father is particularly mentioned in ( John 5:37 ) ; and the thread of the discourse, and the climax, or gradation, here used, show, that it is to be understood of "another man", as Nonnus paraphrases it; of John the Baptist, who is spoken of by name in the next verse, as a witness; and then a greater than he, the works of Christ, and then the Father:
and I know that the witness, which he witnesseth of me, is true;
for John was now alive, though in prison, and continued to bear a testimony to Christ; and therefore he speaks of him as now bearing witness of him, and abiding by that which he had bore; and Christ knew not only that what he testified of him was true in itself, but that his testimony was a valid and authentic testimony, with the generality of the Jews; who held John to be a prophet, and looked upon him as a man of great probity and integrity, and whose word was to be taken: nor indeed could the sanhedrim, before whom Christ now was, object to his character, nor to him as a witness; nor ought they, since they themselves had so judged of him, as appears by their message to him, which Christ next fails not to take notice of.