The term “justification” in theology refers to one of the central concepts of the Protestant Reformation. Classic Catholic doctrine fully taught that God must initiate a person’s turning to Him in faith and repentance. From the earliest church fathers onward all authorized Catholic teachers understood that a human cannot come to Jesus without the Father drawing him. Nevertheless, by the time of Martin Luther the corrupt practices of the Church allowed for the absurd claim that a person could earn (or buy) salvation.
Here is the definition of justification given in Easton’s Bible Dictionary:
“A forensic term, opposed to condemnation. As regards its nature, it is the judicial act of God, by which he pardons all the sins of those who believe in Christ, and accounts, accepts, and treats them as righteous in the eye of the law, i.e., as conformed to all its demands. In addition to the pardon (q.v.) of sin, justification declares that all the claims of the law are satisfied in respect of the justified. It is the act of a judge and not of a sovereign. The law is not relaxed or set aside, but is declared to be fulfilled in the strictest sense; and so the person justified is declared to be entitled to all the advantages and rewards arising from perfect obedience to the law (Romans 5:1-10).
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 (Romans 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 (2 Corinthians 5:21; Romans 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 (Romans 1:17; 3:25, 26; 4:20, 22; Philippians 3:8-11; Galatians 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 (Romans 6:2-7). Good works, while not the ground, are the certain consequence of justification (6:14; 7:6). (see GALATIANS, EPISTLE TO.)”
See also Dead Works.