John 5:31

If I bear witness of myself
Which was not allowed any man to do; nor indeed is it proper that a man should be a witness in his own cause: and, according to the Jewish canons, a man might not be a witness for his wife, because she was reckoned as himself.

``An husband is not to be believed in bearing witness for his wife, that had been carried captive, that she is not defiled, (wmuel dyem Mda Nyav) , "for no man witness of himself" ^F11.''

``a city that is subdued by an army, all the priestesses (or priests' daughters) that are found in it are rejected (from the priesthood, as defiled); but if they have witnesses, whether a servant, or an handmaid, lo, they are to be believed; but no man is to be believed for himself: says R. Zechariah ben Hakatzah, by this habitation (swearing by the temple) her hand was not removed from my hand, from the time the Gentiles entered Jerusalem, till they went out: they replied to him, "no man bears witness of himself".''

my witness is not true,
(Nman al) , not to be believed, or admitted as an authentic testimony: and so the Ethiopic version renders it, "is not credible"; not valid in law, or in such a court of judicature in which Christ now was; for, as according to the Jewish law, no man was admitted a witness for himself, so neither was anything established by a single testimony, but by the mouth of two or three witnesses, ( Deuteronomy 19:15 ) . Christ's meaning is, that his testimony alone, his single witness, how true soever it was, would stand for nothing in their court; and therefore he would not insist upon it, but drop it; for "true" here, is not opposed to that which is "false", but to that which is not valid in law. Christ's testimony was true in itself; nor could it be any other, it coming from him, who is truth itself, the "Amen", and faithful witness; but being considered as an human testimony, and in his own cause, was not to be admitted as sufficient; and this he allows. From arguments, proving his equality with the Father, he passes to testimonies; and without ranking use of his own, he had enough to produce, and which were valid and authentic, and are as follow.