John Chrysostom — as excerpted in the Catena Aurea on John 6:52-54

“(Hom. xlvii. 1) As they thought it impossible that He should do as He said, i. e. give them His flesh to eat, He shews them that it was not only possible, but necessary: Then said Jesus unto them, Verily, verily, I say unto you, Except ye eat the flesh of the Son of man, and drink His blood, ye have no life in you.”