Severus said, “Doctor, there is a certain doctor in Linz who is sorely tried because he cannot find perfect righteousness in himself and because, when he prays, blasphemies against Christ always come to his mind.
“This is a good sign,” Luther replied. “There are two kinds of blasphemy. First, there is active blasphemy when we consciously and intentionally look for reasons to blaspheme, as Faber, the duke of Braunschweig, and the rest do. God keep us from this! But, second, blasphemy is passive when the devil introduces such perverse thoughts into our heads against our will and in spite of our struggle against them. By means of these thoughts God wishes to occupy us so that we don’t get lazy and snore but fight against them and pray. But when the end of life approaches, these temptations cease, for then the Holy Spirit is near to his Christians, keeps the devil at a distance, and gives us a tranquil and quiet mind. (Luther’s Works, v. 54, p.373)