John 3:11 - Coke's Commentary on the Holy Bible

We speak that we do know,— Some have supposed, that, as Christ speaks here in the plural number, he may refer not only to the doctrine which was delivered by himself, but to the testimony which was given to the truth of it by John the Baptist, and to the preaching also of his own disciples, who all concurred in testifying the same things, the certainty of which they were assured of by the teachings of the Spirit, and by their own experience; while it was known to Christ by his omniscience, and by the intimate acquaintance he had with all the counsels of the Father.—And others have supposed that he includes here with himself the Father and the Spirit, who are expressly spoken of in other passages, as being witnesses to the truth of what he said, and as agreeing with him in the testimony that he gave. Compare ch. John 8:18 John 14:20; John 14:26 and 1 John 5:6; 1 John 5:8. But there is no necessity that we should suppose him to refer to any other than himself, since nothing is more usual than for a person of authority to speak of himself in the plural number, as Christ may be observed to have done elsewhere; (Mark 4:30.) and here, in the next verse, he appears to have restrained it to himself, where he says only in the singular number, If I have told you earthly things, &c. In the next clause, and testify that which we have seen, Christ seems to allude to what is mentioned in the law as qualifying a man to be a witness, that he was able to declare of what he had testified, that he had seen or known it, Leviticus 5:1.; and as he therefore had a clear perception and a certain knowledge of the truth of what he said, there was the highest reason to receive his testimony, and to regard him as a true and faithful witness.