John 6:63 - Ellicott's Commentary On The Whole Bible

It is the spirit that quickeneth. — The word “quickeneth,” though it has almost passed from everyday use, will probably hold its place in theological use, and convey for the most part the true meaning. If it is retained here, it must, however, be noted that it is a compound of the word rendered “life” at the close of the verse. “It is the spirit that giveth life... the words... are spirit and are life.” These words are immediately connected with the thought of the Ascension, which was to precede the gift of the Spirit. (Comp. John 7:39; John 16:7 et seq.). We are to find in them, therefore, a deeper meaning than the ordinary one that His teaching is to be, not carnally, but spiritually under-stood. They think of a physical eating of His flesh, and this offends them; but what if they, who have thought of bread descending from heaven, see His body ascending into heaven? They will know then that He cannot have meant this. And the Descent of the Spirit will follow the Ascension of the Son, and men full of the Holy Spirit will have brought to their remembrance all these words (John 14:26), and they will then know what the true feeding on Him is, and these very words which He has spoken will carry their lessons to the inmost being, and be realised, not simply in a spiritual sense, but as spirit and as life.