Whose righteousness is Paul talking about in Romans 3:21?

Les teaches that in verse 21, after the law had only condemned, the text turns with "But now" to a whole different set of circumstances. Christ has died, paid the sin debt, been buried, raised from the dead, and ascended to the Father's right hand, interceding for us. The righteousness being spoken of is specifically the righteousness of God, not of the human individual. It is God's righteousness without the law, which puts legalism out in the cold, and it is manifested, meaning put in the spotlight. It is also witnessed by the law and the prophets, which Les identifies as the Old Testament. He illustrates this by recalling men who wanted no Old Testament taught, and he refused because all Scripture, Old and New, dovetails together.