“Because of this faith in Christ, God seeth not my doubting of His good will towards me, my distrust, heaviness of spirit, and other sins which are yet in me. For as long as I live in the flesh, sin is truly in me. But because I am covered under the shadow of Christ’s wings, as is the chicken under the wing of the hen, and dwell without any fear under that most ample and large heaven of the forgiveness of sins, which is spread over me, God covereth and pardoneth the remnant of sin in me: that is to say, because of that faith wherewith I began to lay hold upon Christ,
He accepteth my imperfect righteousness even for perfect righteousness, and counteth my sin for no sin, which notwithstanding is sin indeed.
So we shroud ourselves under the covering of Christ’s flesh, who is our “cloudy pillar for the day, and our pillar of fire for the night.” (Exod. xiii. 21), lest God should see our sin. And although we see it, and for the same do feel the terrors of conscience, yet flying unto Christ, our mediator and reconciler (through whom we are made perfect) we are sure and safe: for as all things are in Him, so through Him we have all things, who also doth supply whatsoever is wanting in us. When we believe this, God winketh at the sins and remnants of sin yet sticking to our flesh, and so covereth them, as if they were no sin. Because, saith He, thou believest in My Son, although thou has many sins, yet they shall be forgiven thee, until thou be clean delivered from them by death.” Martin Luther, Commentary on Galatians