30 I can of Mine own self do nothing: as I hear, I judge: and My judgment is just; because I seek not Mine own will, but the will of the Father which hath sent Me.
31 If I bear witness of myself, My witness is not true.
32 There is another that beareth witness of Me; and I know that the witness which He witnesseth of Me is true.
I can of My own self do nothing (v.30) — A statement of the Son’s unity with the Father, not an indication of limitation. Jesus Christ has a will, but it is in entire subjection to the Father’s will. That was His nature. The Son can do nothing of Himself, but what He seeth the Father do: for what things soever He doeth, these also doeth the Son likewise (John 5:19).
My judgment is just (v.30) — He will not judge in grace but in absolute righteousness — an answer to any who say a loving God wouldn’t send anyone to hell.
My witness is not true (v.31) — In Jewish law, a self-witness is uncorroborated, invalid and open to suspicion. The Pharisees therefore said unto Him, Thou bearest record of Thyself; Thy record is not true (John 8:13).
My witness is not true — This is an extension of the previous verse — If I bear witness independently of the Father, I have contradicted what I just said. It doesn’t mean that what He says in witness to Himself is untrue. Jesus answered and said unto them, Though I bear record of Myself, yet My record is true: for I know whence I came, and whither I go; but ye cannot tell whence I come, and whither I go. Ye judge after the flesh; I judge no man. And yet if I judge, My judgment is true: for I am not alone, but I and the Father that sent Me (John 8:14-16).
Two or three witnesses were required — At the mouth of two witnesses, or three witnesses, shall he that is worthy of death be put to death; but at the mouth of one witness he shall not be put to death (Deuteronomy 17:6). One witness shall not rise up against a man for any iniquity, or for any sin, in any sin that he sinneth: at the mouth of two witnesses, or at the mouth of three witnesses, shall the matter be established (Deuteronomy 19:15).
another that beareth witness (v.32) — present tense. Jesus wasn’t referring to John the Baptist because he was dead. He’s speaking of the Father who witnessed through John the Baptist, through Scripture, and through Jesus’ works.
the witness He witnesseth of Me is true (v.32) — The Father’s witness is enough. It is true. But to keep with the law, He offers more.
John wrote, in part, to counter the Gnostics who, by 80 AD were already denying Christ’s deity.