Helllo,

Just as the ground of the Christian's justification is Christ's imputed righteousness, which saving benefit every Christian receives the moment he becomes a partaker of Christ through faith, so the ground of the Christian's definitive sanctification is his real spiritual union with Christ in his death, burial, and resurrection into which saving union every Christian actually brought the moment he becomes a partaker with Christ through faith (Rom 6:1-14; 2 Cor 5:14-15). In other words, not only is the Christian accounted righteous vis-a-vis the law, he is also constituted holy by God vis-a-vis the power and mastery of sin. It is not simply positional holiness that is envisioned by definitive sanctification; it is a real existential breach with the reign and mastery of sin, which breach is created by the Christian's actual union with Christ in his death and resurrection, and which is decisive and definite as are Christ's death and resurrection. Murray in his Collected writings has more on this 2:279-280.

This does not mean that the Christian receives personally and existentially, sinless perfection the moment he trusts in Christ: this would leave no room for progressive sanctification (besides the entire sanctification awaits Christ's return 1 Thess 5:23 and of course 1 John 1:8 would apply as well). But, what it does mean is that every Christian, the moment he becomes a Christian, by virtue of his union with Christ, is instantly constituted a "saint" and enters into a new relationship with respect to the former reign of sin in his life and with God himself, in which new relationship he ceases to be a slave to sin and becomes a servant of Christ in God. Commentary by R. Reymond.

Saint Joe grin

Reformed and Always Reforming,