What does Paul mean when he says that Christ became sin on our behalf? I have not found a satisfying answer for this question and I will be talking to my Protestant friends soon about the Mass - I know they will be asking this question. It does seem to say that Christ assumed human sinfulness, doesn't it?
Taken from footnote #30 on page 39 of Not By Bread Alone:
The phrases "to be sin for us" (2 Cor. 5:21); "a curse for us" (Gal. 3:13); "in the likeness of sinful man to be a sin offering" (Rom. 8:3), all express the same truth, that is, Christ became man to be a sacrifice for sin, not that Christ took sin within himself or became sinful. This interpretation was held by the Fathers in consensus, beginning with Justin Martyr and Irenaeus, through Clement of Alexandria, Athanasius, Cyril of Alexandria, Eusebius of Caesarea, Gregory of Nanzianzus, Gregory of Nyssa, John Chrysostom, Ambrose, Augustine, et al., and thorugh the Middle Ages. See S. Lyonnetand L. Sabourin, "Sin, Redemption and Sacrifice," pp. 189-224, for a thorough documentation of the patristic and mediaeval witnesses. Augustine, for example, states: "Those who know the Scriptures of the Old Testament ill approve of what I say. For not once but very often 'sins' there are called 'sacrifices for sins'" (Sermon, 134, IV, 5, PL 38, 745). Aquinas writes: "God made him to be 'sin,' that is, he made him suffer the penalty of sin, when he was offered up for our sins'" (Epistle to the Galatians, III, 5).
Conversely, Martin Luther held that Christ personified sin. On Galatians 3:13 he wrote: "And all the prophets saw this, that Christ was to become the greatest thief, murderer, adulterer, robber, desecrator, blasphemer, etc., there has ever been anywhere in the world... In short, he has and bears all the sins of all men in his body." (D. Martin Luthers Werke: Kritische Gesamtausgabe 2, 517). The extent of his belief is noted here: "Whatever sins I, you, and all of us have committed or may commit in the future, they are as much Christ's own as if he himself had committed them. In short, our sin must be Christ's own sin, or we shall perish eternally" (D. Martin Luthers Werke: Kritische Gesamtausgabe 40, 434). He continues: "It is something awful to bear sin, the wrath of God, the curse, and death. Therefore a man who feels these things in earnest really becomes sin, death, and the curse itself" (D. Martin Luthers Werke: Kritische Gesamtausgabe 40, 448). This coincides with Luther's theory of forensic imputation, wherin Christ is legally imputed with man's sin and man is legally imputed with Christ's righteousness. Since Christ took the whole punishment for sin, works can have no part in justification, since to Luther, works demand legal merit. John Calvin held the same. Of 2 Cor. 5:21 and Is. 53:6 he writes: "...That is, he who was about to cleanse the filth of those iniquities was covered with them by transferred imputation" (Institutes of the Christian Religion 2:16:6). In refutation, Robert Bellarmine wrote: "And as Christ was made a victim for sin in reality and not by imputation, so do we really and not by imputation only share by justification in the effect and similitude of divine justice, when we receive inhering justice" (De Controversiis, vol. IV, lib. II, cap. 10).
Catholic Apologetics International
June 7, 2002