We must press this radical truth further and consider that God's act of justifying the believing sinner is also outside the believer. This may be seen in two different ways. The Meaning of Justification. Justification is a legal word having reference to trial and judgment. It does not mean to make a person subjectively righteous any more than condemnation means to make a person subjectively wicked.
Justification is simply a verdict of the court declaring, or pronouncing, a person to be righteous.
In the case of God's verdict, He declares the believing sinner to be righteous because the sinner's Representative is righteous. Or to put it another way, when the sinner claims the righteousness of Christ as his own and presents it before God, the Judge acknowledges that the debt has been paid, and the sinner is set right before the law. Justification, therefore, is not an act of God within the sinner, but it is an act of God outside the sinner. It is God's verdict upon him. It is a forensic, declaratory act.