2 Corinthians 5:21 → Isaiah 53:6, 10

Paul's most compressed statement of substitution — "God made Him who knew no sin to be sin on our behalf, so that in Him we might become the righteousness of God" — distills the central exchange of Isaiah 53. "Him who knew no sin" echoes 53:9 (no violence, no deceit); "made... to be sin on our behalf" enacts 53:6 ("the LORD has laid on Him the iniquity of us all") and 53:10 (the Servant's soul made an ʾāšām, a guilt/sin offering); and "that we might become the righteousness of God" answers 53:11 ("My righteous Servant will justify many"). The double imputation Paul describes — our sin reckoned to the sinless Servant, his righteousness reckoned to us — is precisely the two-directional movement of the Servant Song, where the LORD lays our iniquity on him and his knowledge justifies us. "To be sin" most plausibly carries the ʾāšām sense of 53:10: Christ becomes the sin offering. The telos is staggering exchange, not moral self-improvement: the believer "becomes the righteousness of God" only by union with the Servant who became sin, so that Christ is treasured as the one in whom an unrighteous sinner is clothed with God's own righteousness.