“Justification is the gracious judgment of God by which he absolves the believer from sin and death, and reckons him righteous and worthy of life for the sake of Christ apprehended in faith (Rom 3.22).”
“This justification comes about because of Christ, but not in the absolute sense of Christ’s being the cause of vocation [calling]. It happens because Christ is apprehended by faith, which follows calling as an effect. Faith precedes justification as the instrumental cause, laying hold of the righteousness of Christ from which justification being apprehended follows; therefore, righteousness is said to be from faith (Rom. 9:30; 10.6). And justification is said to be by faith (Rom. 3.28).”
“That faith is properly called justifying by which we rely upon Christ for the remission of sins and for salvation. For Christ is a sufficient object for justifying faith. Faith justifies only by apprehending the righteousness by which we are justified. That righteousness does not lie in the truth of some proposition to which we give assent, but in Christ alone who has been made sin for us so that we might be righteousness in him (2 Cor. 5.21).”
“Besides the forgiveness of sins there is also required an imputation of righteousness (Rom 5.18, Rev 19.8, Rom 8.3). This is necessary because there might be a total absences of sin in a case where that righteeousness does not exist which must be offered in place of justification.”
A sinner is not justified on the grounds of his faith, nor on the grounds of his deeds, nor on the grounds of a mixture of the two; neither is a sinner justified on the grounds of believing a doctrine (proposition). A sinner is justified by beliving in the person and work of Christ alone. Faith is the Spirit-wrought gift God gives a sinner, a gift which receives all the blessings Jesus has earned for his people. God justifies the ungodly because of Christ’s work imputed to them and their sin imputed to Christ on the cross (2 Cor 5.21). As the Belgic Confession says so well, we are justified by faith even before we do good works, because the works which justify us are Christ’s, not ours (see articles 23-24).