*Minor differences ignored. Grouped by changes, with first version listed as example.
What if you shall see the Son of man ascend to where he was before? The mean and despicable condition of Christ which they saw before their eyes, while, clothed with flesh, he was not at all different from other men, prevented them from submitting to his Divine power; but now -- by withdrawing, as it were, the veil -- he calls them to behold his heavenly glory, as if he had said, "Because I converse among men without honor, I am despised by you, and you recognize in me nothing that is Divine; but ere long God will adorn me with splendid power, and, withdrawing me from the contemptible state of mortal life, will raise me above the heavens." For, in the resurrection of Christ, so great was the power displayed by the Holy Spirit, that it plainly showed Christ to be the Son of God, as Paul also shows, (Romans 1:4.) And when it is said, Thou art my Son, today have I begotten thee, (Psalm 2:7,) the resurrection is brought forward as a proof from which that glory of Christ ought to be acknowledged, and his ascension to heaven was the completion of that glory. When he says that he was formerly in heaven, this does not apply strictly to his human nature, and yet he speaks of the Son of man; but since the two natures in Christ constitute one person, it is not an unusual way of speaking to transfer to one nature what is peculiar to the other.
What and if - Jesus does not say that those who were then present would see him ascend, but he implies that he would ascend. They had taken offence because he said he came down from heaven. Instead of explaining that away, he proceeds to state another doctrine quite as offensive to them - that he would reascend to heaven. The apostles only were present at his ascension, Acts 1:9. As Jesus was to ascend to heaven, it was clear that he could not have intended literally that they should eat his flesh.
If ye shall see the Son of man ascend - Ye need not be stumbled at what I say concerning eating my flesh and drinking my blood, for ye shall soon have the fullest proof that this is figuratively spoken, for I shall ascend with the same body with which I shall arise from the dead; therefore my flesh and blood, far from being eaten by men, shall not even be found among them.
What and if ye shall see the son of man,.... Meaning himself then in a state of humiliation, and was taken for a mere man, though the true Messiah, and Son of God:
ascend up where he was before? for Christ was, he existed before his incarnation, and he was in heaven before; not in his human nature, but as the word and Son of God: and he intimates, that when he had done his work, and the will of his Father, for which he came down from heaven, by the assumption of the human nature, he should ascend up thither again; and which would be seen, as it was, by his apostles; and which would prove that he came down from heaven, as he had asserted; see Ephesians 4:9; and that his flesh and blood were not to be eaten in a corporeal sense; in which sense they understood him: and he hereby suggests, that if it was difficult to receive, and hard to be understood, and was surprising and incredible, that he should come down from heaven, as bread, to be eat and fed upon; it would be much more so to them to be told, that he who was in so mean and lowly a form, should ascend up into heaven.
If ye shall see the Son of man ascend? He points forward to a greater marvel than the one that now staggered before them, the Ascension of the Son of man.
What if ye shall see the Son of man ascend where he was before? - How much more incredible will it then appear to you, that he should give you his flesh to eat?
*More commentary available at chapter level.