The Pharisees therefore said. They adduce as an objection what is commonly said, that no man ought to be trusted, when speaking in his own cause. For a true testimony is put for "what is lawful and worthy of credit." In short, they mean that it is of no use for him to speak, unless he bring proof from some other quarter.

Thou bearest record of thyself - Thou art a witness for thyself, or in thy own case. See John 5:31. The law required two witnesses in a criminal case, and they alleged that as the only evidence which Jesus had was his own assertion, it could not be entitled to belief.
Is not true - Is not worthy of belief, or is not substantiated by sufficient evidence.

Thou bearest record - As if they had said, Dost thou imagine that we shall believe thee, in a matter so important, on thy bare assertion? Had these people attended to the teaching and miracles of Christ, they would have seen that his pretensions to the Messiahship were supported by the most irrefragable testimony.

(5) The Pharisees therefore said unto him, (a) Thou bearest record of thyself; thy record is not true.
(5) Christ is without all exception the best witness of the truth, for he was sent by his Father for that purpose, and his Father showed his approval of him to the world by infinite miracles.
(a) You bear witness of yourself, which is worth nothing in the opinion of all men, and for a man to commend himself is very uncommendable.

The Pharisees therefore said unto him,.... On account of his declaring himself the light of the world: these were either the same who went out of the temple, filled with remorse of conscience, and were now returned, and bearing him a grudge, came to take some advantage against him, if they could; or they were others of the same complexion, sent by them, to make their observations on him:
thou bearest record of thyself. The Ethiopic version renders it, "dost thou thyself?" which does not seem so decent and comely; see Proverbs 27:2; though it does not follow, that what a man says of himself is not truth, as these suggest:
thy record is not true; for John testified of himself, that he was not the Christ, nor Elias, nor that prophet; but the voice of one crying in the wilderness; and this testimony he bore of himself, at the importunity of the Jews themselves, John 1:19; and his testimony was true; so was that which Christ bore of himself; but their sense rather seems to be, that it was not firm and authentic, and would not pass in any court of judicature, since no man can be a witness in his own cause.

bearest record of thyself; thy record is not true--How does He meet this specious cavil? Not by disputing the wholesome human maxim that "self-praise is no praise," but by affirming that He was an exception to the rule, or rather, that it had no application to Him.

My record is true. The Pharisees disputed this. Ordinarily the testimony of a man that he is sent from God is insufficient. He may be deceived, or a deceiver. But Jesus could not be deceived, for he knew all things; nor a deceiver, for he was Truth. Besides, he had other testimony (John 8:18).

Thou testifiest of thyself; thy testimony is not valid - They retort upon our Lord his own words, John 5:31; if I testify of myself, my testimony is not valid. He had then added, There is another who testifieth of me. To the same effect he replies here, John 8:14, Though I testify of myself, yet my testimony is valid; for I am inseparably united to the Father. I know - And from firm and certain knowledge proceeds the most unexceptionable testimony: whence I came, and whither I go - To these two heads may be referred all the doctrine concerning Christ. The former is treated of John 8:16, &c, the latter John 8:21, &c. For I know whence I came - That is, For I came from God, both as God and as man. And I know it, though ye do not.