John 6:63

That quickeneth. Literally, “that which makes alive.” Jesus had been exhorting His hearers to partake of the heavenly food that would give life; now He pointed out even more clearly that such food is spiritual, a fact that His hearers thus far had not realized.

Flesh. This is not the flesh referred to in vs. 51-56. There Christ’s flesh and blood are used together in speaking of the spiritual sustenance received by the one who partakes of the life of his Lord. Here the word “flesh” is used in a different context; it is contrasted with “spirit,” and thus clearly refers to the material things of this life, and particularly to material food, which cannot sustain eternal, spiritual life.

Speak. Textual evidence attests (cf. p. 146) the reading “I have spoken.” The reference is thus directly to the words of this discourse that Jesus had just spoken, and indeed, was still speaking.

They are spirit. The truths Christ uttered are concerned with spiritual things, and to receive them into the heart by faith is to receive spiritual life (see on ch. 3:16; cf. ch. 17:3).