John 5:31

If any one unpracticed in the art undertake to work a mine, he will get no gold, but confounding all aimlessly and together, will undergo a labor unprofitable and pernicious: so also they who understand not the method of Holy Scripture, nor search out its peculiarities and laws, but go over all its points carelessly and in one manner, will mix the gold with earth, and never discover the treasure which is laid up in it. I say this now because the passage before us containeth much gold, not indeed manifest to view, but covered over with much obscurity, and therefore by digging and purifying we must arrive at the legitimate sense. For who would not at once be troubled at hearing Christ say, "If I testify of Myself, My witness is not true"; inasmuch as He often appeareth to have testified of Himself? For instance, conversing with the Samaritan woman He said, "I Am that speak unto thee": and in like manner to the blind man, "It is He that talketh with thee"; and rebuking the Jews, "Ye say, thou blasphemest, because I said I am the Son of God." And in many other places besides He doth this. If now all these assertions be false, what hope of salvation shall we have? And where shall we find truth when Truth Itself declareth, "My witness is not true"? Nor doth this appear to be the only contradiction; there is another not less than this. He saith farther on, "Though I bear witness of Myself, yet My witness is true"; which then, tell me, am I to receive, and which deem a falsehood? If we take them out thus [from the context] simply as they are said, without carefully considering the person to whom nor the cause for which they are said, nor any other like circumstances, they will both be falsehoods. For if His witness be "not true," then this assertion is not true either, not merely the second, but the first also. What then is the meaning? We need great watchfulness, or rather the grace of God, that we rest not in the mere words; for thus the heretics err, because they enquire not into the object of the speaker nor the disposition of the hearers. If we add not these and other points besides, as times and places and the opinions of the listeners, many absurd consequences will follow.

The Jews were about to object to Him, "If thou bearest witness concerning thyself, thy witness is not true": therefore He spake these words in anticipation; as though He had said, "Ye will surely say to Me, we believe thee not; for no one that witnesseth of himself is readily held trustworthy among men." So that the "is not true" must not be read absolutely, but with reference to their suspicions, as though He had said, "to you it is not true"; and so He uttered the words not looking to His own dignity, but to their secret thoughts. When He saith, "My witness is not true," He rebuketh their opinion of Him, and the objection about to be urged by them against Him; but when He saith, "Though I bear witness of Myself, My witness is true," He declareth the very nature of the thing itself, namely, that as God they ought to deem Him trustworthy even when speaking of Himself.

For since He had spoken of the resurrection of the dead, and of the judgment, and that he that believeth on Him is not judged, but cometh unto life, and that He shall sit to require account of all men, and that He hath the same Authority and Power with the Father; and since He was about again otherwise to prove these things, He necessarily put their objection first. "I told you," He saith, "that 'as the Father raiseth the dead and quickeneth them, so the Son quickeneth whom He will'; I told you that 'the Father judgeth no man, but hath committed all judgment unto the Son'; I told you that men must 'honor the Son as they honor the Father'; I told you that 'he that honoreth not the Son honoreth not the Father'; I told you that 'he that heareth My words and believeth them shall not see death, but hath passed from death unto life'; that My voice shall raise the dead, some now, some hereafter; that I shall demand account from all men of their transgressions, that I shall judge righteously, and recompense those who have walked uprightly." Now since all these were assertions, since the things asserted were important, and since no clear proof of them had as yet been afforded to the Jews but one rather indistinct, He putteth their objection first when He is about to proceed to establish His assertions, speaking somewhat in this way if not in these very words: "Perhaps ye will say, thou assertest all this, but thou art not a credible witness, since thou testifiest of thyself." First then checking their disputatious spirit by setting forth what they would say, and showing that He knew the secrets of their hearts, and giving this first proof of His power, after stating the objection He supplieth other proofs clear and indisputable, producing three witnesses to what He said, namely, the works wrought by Him, the witness of the Father, and the preaching of John.

(de Verb. Dom. s. 43) He knew Himself that His witness of Himself was true, but in compassion to the weak and unbelieving, the Sun sought for candles, that their weak sight might not be dazzled by His full blaze. And therefore John was brought forward to give his testimony to the truth. Not that there is such testimony really, for whatever witnesses bear witness to Him, it is really He who bears witness to Himself; as it is His dwelling in the witnesses, which moves them so to give their witness to the truth.

Or thus; Christ, being both God and man, He shows 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?