"If the first inward thought is not warded off, it will generate a desire, then his desire will generate a wish, and the wish will generate an intention, and the intention will generate the action, and the action will result in ruin and divine wrath. So evil must be cut off at its root, which is when it is simply a thought that crosses the mind, from which all the other things follow on."

-Imam Abu Hamid al-Ghazzali (Ihyaa Uloom al-Deen 6/17-