For nature and weak faith cannot, indeed, abstain from these, just as it cannot easily divest itself of other emotions such as impatience, wrath, and concupiscence. But they should remain only thoughts; they should not become axioms that are fixed and speak the final word or are established by our judgment and conscience. I cannot prevent my heart from being disturbed by strange vexations. Hence one should follow the advice of the hermit to whom a youth complained that he rather often experienced imaginations concerned with lusts and other sins and to whom the old man replied: “You cannot prevent the birds from flying over your head. But let them only fly and do not let them build nests in the hair of your head. Let them be thoughts and remain such; but do not let them become conclusions.” It is the mark of desperate men like Saul, Judas, and others to make conclusions out of thoughts, saying: “My punishment is greater than I can bear” (Gen. 4:13) and likewise: “I have betrayed innocent blood” (cf. Matt. 27:4). These men throw away the Word, faith, and prayer. That is making judicial sentences out of temptation.

Luther, AE 6, on Genesis 32