17 “For my flesh,” says He, “is meat indeed, and my blood is drink indeed.” For while by meat and drink men seek to attain to this, neither to hunger nor thirst, there is nothing that truly affords this, except this meat and drink, which does render them by whom it is taken immortal and incorruptible; that is, the very fellowship of the saints, where will be peace and unity, full and perfect. Therefore, indeed, it is, even as men of God understood this before us, that our Lord Jesus Christ has pointed our minds to His body and blood in those things, which from being many are reduced to some one thing. For a unity is formed by many grains forming together; and another unity is effected by the clustering together of many berries.
Source: Tractates on the Gospel of John (New Advent)