James Buchanan: Christ's righteousness is the only and all sufficient righteousness, on the grounds of which we can be justified before God

That righteousness [which is the ground of a sinner's Justification] is called in Scripture "the righteousness of God"; "the righteousness of Christ"; the "righteousness of One"; "the obedience of One"; the "free gift unto justification of life"; "the righteousness which is of" or "by" or "through faith"; "the righteousness of God without the law"; and "the righteousness which God imputes without works."

It will be found that, while these various expressions are descriptive of its different aspects and relations, they are all employed with reference to the same righteousness -- that there is one righteousness in which they all find their common center, as so many distinct rays converging towards the same focus, while each retains its distinctive meaning -- and that there is no other righteousness to which they can all be applied or in which they can find their adequate explanation.

... By His [Christ's] vicarious sufferings and obedience, He fulfilled the Law both in its precept and its penalty and is now said to be 'the end of the law for righteousness to every one that believeth,' while His righteousness is identified with 'the righteousness of God,' to which the unbelieving Jews refused to 'submit themselves' and contrasted with 'their own righteousness' which they 'went about to establish,' 'as it were by the works of the law' (Rom 10:3-4)."

-Dr. James Buchanan, "The Immediate and Only Ground of Justification: The Imputed Righteousness of Christ"