Just as the head and body of a man form one single man, so the Son of the Virgin and those he has chosen to be his members form a single man and the one Son of Man. Christ is whole and entire, head and body, say the Scriptures, since all the members form one body, which with its head is one Son of Man, and he with the Son of God is one Son of God, who himself with God is one God. Therefore the whole body with its head is Son of Man, Son of God, and God. This is the explanation of the Lord’s words: Father, I desire that as you and I are one, so they may be one with us.
Emphasis in bold print is mine.