For Irenaeus, Paul's presentation of the Old Law (the Mosaic covenant) in this passage indicates that the Old Law revealed humanity's sinfulness but could not save them. He explains that "For as the law was spiritual, it merely made sin to stand out in relief, but did not destroy it. For sin had no dominion over the spirit, but over man." Since humans have a physical nature, they cannot be saved by a spiritual law. Instead, they need a human Savior. This is why it was necessary for Christ to take human flesh. Irenaeus summarizes how Christ's taking human flesh saves humanity with a statement that closely resembles Romans 5:19, "For as by the disobedience of the one man who was originally moulded from virgin soil, the many were made sinners, and forfeited life; so was it necessary that, by the obedience of one man, who was originally born from a virgin, many should be justified and receive salvation." The physical creation of Adam and Christ is emphasized by Irenaeus to demonstrate how the Incarnation saves humanity's physical nature.