(28) Then said Jesus unto them.--Better, There-fore . . . The teaching arises immediately out of the want of understanding just mentioned.

When ye have lifted up the Son of man.--Better, When ye shall have lifted up . . . (Comp. Notes on John 3:14; John 6:62; John 12:32; John 12:34.) Both the Crucifixion and Ascension are implied here. Now. for the first time, they are marked out as the instruments of the Crucifixion (comp. Acts 3:15), and therefore the means by which He will return to His Father's throne.

Then shall ye know . . .--These words confirm the view that the teaching of these verses arises immediately out of their present ignorance. Then the veil will be removed. Then the death of Christ will be followed by His glory. As we read these words they impress us with that calm of assured certainty with which they are uttered (comp. John 8:12) before the events, and reminds us of the signal way in which they were fulfilled. (Comp., e.g., Notes on Matthew 23:39 and Acts 2:37.)

That I am he.--Comp. Note on John 8:24.

And that I do nothing of myself.--This is dependent on "know that" in the previous clause; as is the remainder of the verse, and probably the first clause of the following verse also. They will then know that He is divine, and that the acts and words which they cannot now understand are part of the divine life in union with the Father. Now they marvel and ask, "How knoweth this man letters, having never learned?" (John 7:15): then they shall know that according as the Father taught Him, He spake these things. Now they cannot understand the witness of the Father (John 8:19): then they shall know that He that sent Him was with Him.

Verse 28. - But when Jesus turns to them again he calls special attention to the main source of their continuous misconception and rejection. Not only is he "the Son," and "the Son of God," but indubitably he is also "the Son of man." He has come down from heaven and is before them as a Man among men - "one Jesus." He has taken upon himself the form of a slave, the fashion of man. That the manifestation of the Divine should be perfectly realized in the human, though a fundamental truth lying at the heart of all revelation, is nevertheless not the alphabet of Divine teaching; nay, it is the very highest and most recondite of all truths. This humbled humanity of the incarnate Logos led on to other issues of enormous significance. The eternal Son in the form of God would become, as "Son of man," obedient unto death. The highest revelation of the Son of God, and therefore of the Father, would be effected by the surrender of that mysterious life of his for the world's behoof. The previous announcements of this truth, which we now see to be the very crown and culmination of the gospel, had greatly offended his hearers of all kinds, and on distinct grounds. In the words that follow a touch of deeper meaning than any which had preceded is supplied when he proceeds to associate this death of the Son of man with the wilful act of the ecclesiastical authorities in Jerusalem. Jesus therefore said (unto them), When ye shall have lifted up the Son of man (compare here notes on John 3:14; 6:62; 12:32). The word ὑψόω is used with the twofold sense of exaltation on the cross" signifying by what death he should glorify God" - and also of the issues of that lifting up by means of the tree of ignoble torment and mortal agony to the throne of glory. The twofold meaning of the word cannot be excluded here. Then ye shall come to know - then the process of proof will be completed - that I am (he) - that I am that which fundamentally I am declaring to you, that my testimonies have unique but trenchant confirmation - and that I am doing nothing from myself, but that even as the Father taught me, (so) these things I speak. The "he that sent me" (ver. 26), is here replaced by "the Father." "The things which I heard from (παρὰ) him" is replaced by "even as the Father taught me," and the ταῦτα λαλῶ are repeated. "The cross and the crown" will be the proof to the most obtuse and bigoted "that I am that which I say I am." The forecast is here given of the conversion of his murderers, the overwhelming effects produced by the resurrection and the ascension of Jesus, and the gift of the Holy Ghost (Acts 2:36; Acts 4:4; Acts 6:7; Romans 11:11). Bengel: "Cognoscetis ex re, quod nunc ex verbo non creditis."

8:21-29 Those that live in unbelief, are for ever undone, if they die in unbelief. The Jews belonged to this present evil world, but Jesus was of a heavenly and Divine nature, so that his doctrine, kingdom, and blessings, would not suit their taste. But the curse of the law is done away to all that submit to the grace of the gospel. Nothing but the doctrine of Christ's grace will be an argument powerful enough, and none but the Spirit of Christ's grace will be an agent powerful enough, to turn us from sin to God; and that Spirit is given, and that doctrine is given, to work upon those only who believe in Christ. Some say, Who is this Jesus? They allow him to have been a Prophet, an excellent Teacher, and even more than a creature; but cannot acknowledge him as over all, God blessed for evermore. Will not this suffice? Jesus here answers the question. Is this to honour him as the Father? Does this admit his being the Light of the world, and the Life of men, one with the Father? All shall know by their conversion, or in their condemnation, that he always spake and did what pleased the Father, even when he claimed the highest honours to himself.Then said Jesus unto them,.... Upbraiding them with their ignorance, and giving them a sign, as well as pointing out the time when they either, by good or sad experience, should have knowledge of him:

when ye have lift up the son of man; meaning himself, who was to be lifted up upon the cross, as the serpent was upon the pole, in the wilderness; and which signified the manner of death he should die, the death of the cross; and suggested, that what the Jews designed for his reproach, shame, and abasement, would be the way and means of his rise and exaltation; and this lifting him up, or crucifying him, he ascribes to them, because they would deliver him to Pontius Pilate to be condemned, and stir up the people to ask, and be importunate themselves for his crucifixion:

then shall ye know that I am he; the Son of God, and true Messiah, as the centurion, and those that were with him, did, when they observed the earthquake; and the things that were done at his death; and after the death, resurrection, and ascension of Christ, and the pouring forth of his Spirit, many of the Jews had not only a notional, but a true and spiritual knowledge of Jesus, as the Messiah; and upon the destruction of their temple, city, and nation, and their disappointment by false Christs, they doubtless many of them must, and did know, that the true Messiah was come, and that Jesus of Nazareth was he:

and that I do nothing of myself; See Gill on John 5:19;

but as my Father hath taught me, I speak these things; this he says not as lessening himself, or making himself inferior to the Father, but to show the excellency of his doctrine, and to assert the original, authority, and divinity of it; suggesting that it was not an human doctrine, or a device of man's, or his own, as man, but was divine, and from God; see John 7:16.