John Gill Commentary John 6:58

"This is the bread which came down out of heaven: not as the fathers ate, and died; he that eateth this bread shall live for ever." — John 6:58 (ASV)

This is that bread which came down from heaven
That true bread, the bread of God, the bread of life, living bread; meaning himself, as in (John 6:32John 6:33John 6:35John 6:48John 6:50John 6:51) ;

not as your fathers ate manna, and are dead :
this is bread of a quite different nature from that; that was only typical bread, this true; that was the bread of angels, but this is the bread of God; that came but from the air, this from the third heaven; that men ate of, and died; but whoever eats of this, lives for ever; see (John 6:49) ; as follows:

he that eats of this bread shall live for ever ;
(See Gill on John 6:51).