2 Corinthians 5:21

For he hath made him to be sin for us Literally, He made, i.e. in the Sacrifice on the Cross. The word sinhas been variously explained as a sin-offering, a sinner, and so on. But it is best to take the word in its literal acceptation. He made Him to be sin, i.e. appointed Him to be the representative of sin and sinners, treated Him as sin and sinners are treated (cf. 2 Corinthians 5:15). He took on Himself to be the representative of Humanity in its aspect of sinfulness (cf. Romans 8:3; Philippians 2:7) and to bear the burden of sin in all its completeness. Hence He won the right to represent Humanity in all respects, and hence we are entitled to be regarded as God's righteousness (which He was) not in ourselves, but in Him as our representative in all things. See also 2 Corinthians 5:14.

who knew no sin Cf. Hebrews 4:15; 1 Peter 2:22; 1 John 3:5; also John 8:46.

that we might be made the righteousness of God in him We not only are regarded as God's righteousness, but become so, by virtue of the inward union effected between ourselves and Him by His Spirit, through faith. See 2 Corinthians 5:17 and note. "He did not say righteous, but righteousness, and that the righteousness of God." Chrysostom. See also Bp Wordsworth's note. Cf. Romans 1:17; Romans 3:22; Romans 5:19; Romans 10:3; 1 Corinthians 1:30.