14 The words in which we speak of the things of God must be used in no mere human and worldly sense, nor must the perverseness of an alien and impious interpretation be extorted from the soundness of heavenly words by any violent and headstrong preaching. Let us read what is written, let us understand what we read, and then fulfil the demands of a perfect faith. For as to what we say concerning the reality of Christ's nature within us, unless we have been taught by Him, our words are foolish and impious. For He says Himself, My flesh is meat indeed, and My blood is drink indeed. He that eats My flesh and drinks My blood abides in Me, and I in him. As to the verity of the flesh and blood there is no room left for doubt. For now both from the declaration of the Lord Himself and our own faith, it is verily flesh and verily blood. And these when eaten and drunk, bring it to pass that both we are in Christ and Christ in us. Is not this true? Yet they who affirm that Christ Jesus is not truly God are welcome to find it false. He therefore Himself is in us through the flesh and we in Him, while together with Him our own selves are in God.
Source: On the Trinity (New Advent)