Let us rejoice and give thanks. Not only are we become Christians, but we are become Christ. My brothers, do you understand the grace of God that is given us? Wonder, rejoice, for we are made Christ! If He is the Head, and we the members, then together He and we are the whole man.... This would be foolish pride on our part, were it not a gift of his bounty. But this is what He promised by the mouth of the Apostle: You are the body of Christ, and severally His members (1 Cor. 12:27).
p. 415 - On the Mystical Body of Christ