Born around 350 and dying in exile from his See, Constantinople, in 407, John Chrysostom, contemporary of Ambrose and Augustine, is the great figure of the Eastern Church in the fourth century. His doctrine on the Eucharist was marked by its very realistic references to the Presence of Christ in the Sacrament and to his many references to the sacrificial nature of the Lord's Supper. His words on the theme are abundant. Typical of them are the following from his Homily 82 on the Gospel of Matthew, where he comments on the institution of the Eucharist as found in Matthew 26.

Let us therefore everywhere be attentive to God. Let us not contradict him although what he says appears to be contrary to our reasoning and understanding. Thus we carry out in the Mysteries not only what appears to our senses but what his words tell us. For his word is not able to deceive; our senses are easily deceived. Because the Word says, "This is my Body", let us be attentive, let us believe, let us look upon him with the eyes of the spirit. For Christ did not give us something sensible; even in the sensible things, all is spiritual... How many there are who still say, "I want to see his shape, his image [Gk. ton tupon], his clothing, his sandals." Behold, you do see him, you touch him, you eat him!... Therefore let everyone be vigilant. No small punishment hangs over him who communicates unworthily. Think of how angry you become against the traitor and against those who crucified Christ. And so beware lest you yourself be guilty of the Body and Blood of Christ.

The Hidden Manna: A Theology of the Eucharist
Fr. James T. O'Connor