Presumptuous sins may be one of the most menacing troubles of the professed Christian. There was a cartoon about a childish character told not to do something, his reply was, “If I do’d it, I get a spankin.’ I do’d it.” That is presumptuous sin. We know that to do something, God considers sin with the attitude that God will let it slide, or “Oh, well, His grace will cover it,” is the type of sin God abhors. It presumes that God is merciful but not just; He is gracious but not righteous. This sin exposes wickedness in the heart, “Why does the wicked man revile God? Why does he say to himself, "He won't call me to account"? (Psalm 10:13, NIV)
The Psalmist pleads with the Lord to “keep” him from presumptuous sin because he knows that it is all too easy to presume upon the loving kindness of the Lord, forgetting that a holy, righteous God, though gracious, still hates sin and will judge the deeds of all men. Selah.