23 This is the wish of our schoolmaster the law, of the prophets who intervened between Christ and the law, of Christ who is the fulfiller and end of the spiritual law; of the emptied Godhead, of the assumed flesh, of the novel union between God and man, one consisting of two, and both in one. This is why God was united to the flesh by means of the soul, and natures so separate were knit together by the affinity to each of the element which mediated between them: so all became one for the sake of all, and for the sake of one, our progenitor, the soul because of the soul which was disobedient, the flesh because of the flesh which co-operated with it and shared in its condemnation, Christ, Who was superior to, and beyond the reach of, sin, because of Adam, who became subject to sin.
Source: Orations (New Advent)