For he has made him, who knew no sin, to be sin for us; that we might be made the righteousness of God in him.
All Commentaries on 2 Corinthians 5:21 Go To 2 Corinthians 5
Cyril of Alexandria
AD 444
We do not say that Christ became a sinner, far from it, but being righteous (or rather, righteousness, because he did not know sin at all), the Father made him a victim for the sins of the world.
