Charles Ellicott Commentary John 8:28

"Jesus therefore said, When ye have lifted up the Son of man, then shall ye know that I am [he], and [that] I do nothing of myself, but as the Father taught me, I speak these things." — John 8:28 (ASV)

Then Jesus said to them.—Better, Therefore... The teaching arises immediately out of the lack of understanding just mentioned.

When you have lifted up the Son of man.—Better, When you will have lifted up... (Compare 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 , and therefore the means by which He will return to His Father’s throne.

Then you will 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 before the events. They also remind us of the remarkable way in which they were fulfilled (compare, for example, Notes on Matthew 23:39 and Acts 2:37).

That I am he.—Compare 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 will know that just as the Father taught Him, He spoke these things.

Now they cannot understand the witness of the Father (John 8:19); then they will know that He who sent Him was with Him.