The meritorious ground of our justification is the blood of Christ (Rom. 5:9). But had He, who was "made of a woman, made under the law," failed in any one point in keeping it, He would not have been the holy Lamb of God, who could have atoned by His death for our sins. Now it is clear that we were not justified by His keeping the law for us, for " if righteousness come by law, then Christ is dead in vain" (Gal. 2:21). We should have been justified before He died in that case. This shows the mistake of such thoughts.
On the teaching of God imputing righteousness, Scripture is clear. Faith, not the obedience of Christ, is imputed to us for righteousness (Rom. 4:5; Gal. 3:6; James 2:23); that God reckons the man righteous, who believes His testimony, whatever it may be. In Abraham's case it was God's testimony as to his seed: in ours it is His testimony about the work of His Son (Rom. 4:19-25),
" Obedience " (ὑπαχοή) may, of course, often be used with reference to continued obedience, but in Rom. 5:19, it refers to only one act, as the preceding verse distinctly states, "Therefore as by one offense, unto all to condemnation: so by one righteousness (διχαίωμα), unto all men unto justification of life."