JESUS was “made sin for us” (2 Corinthians 5:21). Besides being grammatically impossible, we must reject as futile … the suggestion that by “sin” Paul in this place means “sin-offering”. No, Paul means sin, but we must understand what is intended by the word. Christ was made sin in partaking of the nature in which sin reigns and which produces sin, and which therefore by metonymy is called sin. We may go further and say he was made “sin” in enduring the consequences of sin – sin not his own, for he did not sin – but sin which has left its effects upon the whole race of mankind in bringing all under subjection to death. If we recognise how horrible in God’s sight sin is, then we see how the effects of it are brought to a focus as it were in His own obedient Son. “Him who knew no sin God made to be sin for us, that we might become the righteousness of God in him.”
JOHN CARTER, The Letter to the Galatians, page 75.