And this righteousness from God comes through faith in Jesus Christ to all who believe. There is no distinction,
22. Even the righteousness of God, etc. The words which follow, διὰ πίστεως Ιησοῦ Χριστοῦ “by or through the faith of Jesus Christ,” mean not the faith which is his, but the faith of which he is the object. They ought to be rendered “through faith in Jesus Christ.” The genitive case has often this meaning: “Εχετε πίστιν Θεοῦ — Have faith in (of) God,”...
From all this Paul infers that it is in vain to look for justification by the works of the law, and that it is to be had only by faith, which is the point he has been all along proving, from Rom 1:17, and which he lays down (Rom 3:28) as the summary of his discourse, with a quod erat demonstrandum - which was to be demonstrated.
Commenting on Romans 3:19-31
To declare, I say, at this time, his righteousness,.... This end is further explained, it being to declare the righteousness of God "at this time", under the Gospel dispensation; in which there was such a display of the grace, mercy, and goodness of God: that he might be just; that is, appear to be so: God is naturally and essentially just in himself; and he...