As Christ voluntarily took upon Himself our death, which is the effect of sin, whereas He had no sin Himself, in order to deliver us from death, and to make us to die spiritually unto sin, so also He took upon Himself circumcision, which was a remedy against original sin, whereas He contracted no original sin, in order to deliver us from the yoke of the Law, and to accomplish a spiritual circumcision in us--in order, that is to say, that, by taking upon Himself the shadow, He might accomplish the reality.
St. Thomas Aquinas, ST 3.37.1ad3
