This is what is meant when we insist that justification is forensic. It has to do with a judgment given, declared, pronounced; it is judicial or juridical or forensic. The main point of such terms is to distinguish between the kind of action which justification involves and the kind of action in regeneration. Regeneration is an act of God in us; justification is an act of God with respect to us. The distinction is like that of the distinction between the act of a surgeon and the act of a judge. The surgeon, when he removes an inward cancer, does something in us. That is not what a judge does—he gives a verdict regarding our judicial status. If we are innocent he declares accordingly.
The purity of the gospel is bound up with the recognition of this distinction. If justification is confused with regeneration or sanctification, then the door is opened for the perversion of the gospel at its center. Justification is still the article of the standing or falling church.
John Murray, Redemption Accomplished and Applied (Grand Rapids: Eerdmans, 1955), 127–28 (HT: Mike Mattingly Jr)