The Text Says So
“Gundry’s antithesis is perplexing: the wisdom is God’s, he says, not Christ’s, even though the text says ‘Christ has become for us wisdom’ and ‘Christ has become for us … righteousness,’ [1 Cor. 1:30] and so forth. Again, this is bound up with the language of union in Christ: ‘you are in Christ Jesus.’ Nevertheless, the next word is a relative pronoun whose referent is Christ, who is explicitly said to have become our righteousness. Why, then, the complete antithesis (‘God’s, not Christ’s’)? This is not far removed from the ideas found in 2 Corinthians 5:19–21: God was in Christ, reconciling the world to himself. So yes, this righteousness is God’s; and yes, this righteousness is Christ’s. The text says so.”
[D. A. Carson, “The Vindication of Imputation,” in Husbands & Treier, Justification: What’s at Stake in the Current Debate]