It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life. It is the spirit that quickeneth - It is the spiritual sense only of my words that is to be attended to, and through which life is to be attained, 2 Corinthians 3:6. Such only as eat and drink what I have mentioned, in a spiritual sense, are to expect eternal life.
The flesh profiteth nothing - If ye could even eat my flesh and drink my blood, this would not avail for your salvation. These words contain a caution that the hearers should not understand his words in the strict literal sense, as if his body were really Bread, and as if his flesh and blood were really to be eaten and drank.
The words that I speak - Or, I have spoken. Instead of λαλω, I speak, I read λελαληκα, I have spoken, on the authority of BCDKLT, thirteen others; the Syriac, all the Arabic, all the Persic, Coptic, Ethiopic, Gothic, Slavonic, Vulgate, all the Itala; Origen, Eusebius, Athanasius, Basil, Cyril, Chrysostom, Tertullian, Ambrosias, Augustin, Gaudentius, and Vigilius Taps. This is an important reading, and plainly shows that our Lord's words here do not refer to any new point of doctrine which he was then inculcating, but to what he had spoken concerning his being the living bread, and concerning the eating of his flesh, and drinking of his blood, in the preceding verses.
Are spirit, and they are life - As my words are to be spiritually understood, so the life they promise is of a spiritual nature: see Bishop Pearce.