John Chrysostom — as excerpted in the Catena Aurea on John 6:60-71

“(Hom. xlvii. 2) The revelation however of these hidden things was a mark of His Divinity: hence the meaning of what follows; And if ye shall see the Son of man ascend up where He was before; supply, What will ye say? He said the same to Nathanael, Because I said to thee, I saw thee under the fig tree, believest thou? Thou shalt see greater things than these. He does not add difficulty to difficulty, but to convince them by the number and greatness of His doctrines. For if He had merely said that He came down from heaven, without adding any thing further, he would have offended His hearers more; but by saying that His flesh is the life of the world, and that as He was sent by the living Father, so He liveth by the Father; and at last by adding that He came down from heaven, He removed all doubt. Nor does He mean to scandalize His disciples, but rather to remove their scandal. For so long as they thought Him the Son of Joseph, they could not receive His doctrines; but if they once believed that He had come down from heaven, and would ascend thither, they would be much more willing and able to admit them.”