ISB ~ John 6 v63

the Spirit … the flesh:A contrast between the Spirit’s ability to enlighten our minds (14:26) and human reason’s inability to comprehend revealed truths apart from faith (8:15). It is this earthbound perspective that is profitless in the face of divine mysteries. Note that Jesus is not speaking of his own “flesh”, which does in fact give life to the world (6:51; Eph 2:13-16; Heb 10:10) (CCC 737).