Albert Barnes Commentary John 6:63

"It is the spirit that giveth life; the flesh profiteth nothing: the words that I have spoken unto you are spirit, are are life." — John 6:63 (ASV)

It is the Spirit that quickeneth. These words have been understood in different ways. The word "Spirit" here evidently does not refer to the Holy Spirit, for He adds, The words that I speak unto you, they are spirit. He refers here, probably, to the doctrine He had been teaching in opposition to their notions and desires. "My doctrine is spiritual; it is fitted to give life to and nourish the soul. It is from heaven. Your doctrine or your views are earthly, and may be called flesh, or fleshly, as pertaining only to the support of the body. You place great value on the doctrine that Moses fed the body; yet that did not permanently profit, for your ancestors are dead. You also seek food from Me, but your views and desires are coarse and earthly."

Quickeneth. Gives life. (See Barnes on John 5:21).

The flesh. Your carnal views and desires, and the literal understanding of My doctrine. By this Jesus shows them that He did not intend that His words should be taken literally.

Profiteth nothing. It would not serve the real needs of humanity. The bread that Moses gave, the food which you seek, would not be of real value to humanity's highest needs.

They are spirit. They are spiritual. They are not to be understood literally, as if you were really to eat My flesh, but they are to be understood as denoting the need for that provision for the soul which God has made by My coming into the world.

Are life. Are fitted to produce or give life to the soul dead in sins.