The cup of blessing which we bless, is it not the communion of the blood of Christ? The bread which we break, is it not the communion of the body of Christ?
All Commentaries on 1 Corinthians 10:16 Go To 1 Corinthians 10
Augustine of Hippo
AD 430
That chalice, or rather, what the chalice holds, consecrated by the word of God, is the blood of Christ. Through those elements the Lord wished to entrust to us his body and the blood which he poured out for the remission of sins. If you have received worthily, you are what you have received.