If we have sinned, it is wonderful consciously to say, ‘Thank you for a completed work,’ after we have brought that specific sin under the finished work of Christ. The conscious giving of thanks brings assurance and peace. We say, ‘Thank you’ for work completed upon the cross, which is sufficient for a completely restored relationship.
This isn’t on the basis of my emotions, any more than in my justification. The basis is the finished work of Christ in history and the objective promises of God in the written Word. If I believe Him, and if I believe what He has taught me about the sufficiency of the work of Christ for restoration, I can have assurance, no matter how black the blot has been. This is the Christian reality of salvation from one’s conscience.
For myself, through the thirty years or so since I began to struggle with this in my own life, I picture my conscience as a big black dog with enormous paws which leaps upon me, threatening to cover me with mud and devour me. But as this conscience of mine jumps upon me, after a specific sin has been dealt with on basis of Christ’s finished work, then I should turn to my conscience and say, in effect, ‘Down! Be still!’ I am to believe God and be quiet.
— Francis Schaeffer True Spirituality
(HT: Of First Importance)