Meaning
It proceeds on the imputing or crediting to the believer by God himself of the perfect righteousness, active and passive, of his Representative and Surety, Jesus Christ (Rom 10:3-9). Justification is not the forgiveness of a man without righteousness, but a declaration that he possesses a righteousness which perfectly and for ever satisfies the law, namely, Christ's righteousness (2Cor 5:21; Rom 4:6-8).
The sole condition on which this righteousness is imputed or credited to the believer is faith in or on the Lord Jesus Christ. Faith is called a "condition," not because it possesses any merit, but only because it is the instrument, the only instrument by which the soul appropriates or apprehends Christ and his righteousness (Rom 1:17; 3:25, 26; 4:20, 22; Phil 3:8-11; Gal 2:16).
The act of faith which thus secures our justification secures also at the same time our sanctification (q.v.); and thus the doctrine of justification by faith does not lead to licentiousness (Rom 6:2-7). Good works, while not the ground, are the certain consequence of justification (6:14; 7:6). (See GALATIANS, EPISTLE TO.)