25 Then they said to Him, "Who are You?" And Jesus said to them, "Just what I have been saying to you from the beginning.
26 I have many things to say and to judge concerning you, but He who sent Me is true; and I speak to the world those things which I heard from Him."
27 They did not understand that He spoke to them of the Father.
28 Then Jesus said to them, "When you lift up the Son of Man, then you will know that I am He, and that I do nothing of Myself; but as My Father taught Me, I speak these things.
29 And He who sent Me is with Me. The Father has not left Me alone, for I always do those things that please Him."
30 As He spoke these words, many believed in Him.
just what I have been saying (v. 25) — He had already explained, He didn't need to do so again. I have spoken of light — I AM that light. I have spoken of truth — I AM that truth. They didn't understand, but we can — And we know that the Son of God has come and has given us an understanding, that we may know Him who is true; and we are in Him who is true, in His Son Jesus Christ. This is the true God and eternal life (1 John 5:20).
I have many things to say (v. 26) — or "many things I could say" concerning them, and His words would be a judgment.
lift up (v. 28) — the cross
then you will know (v. 28) — when judgment comes upon the unbelieving nation (Some would believe after His death, at Pentecost).
The Father was with Him (vs. 16, 29). He did nothing of His own will (vs. 28, 42).