Ан-Нас 114:5

Verse [ 114:4] مِن شَرِّ‌ الْوَسْوَاسِ الْخَنَّاسِ (from the evil of the whisperer who withdraws [ when Allah's name is pronounced ].) After invoking three attributes of Allah, the present verse describes the one from whom protection is sought. He is 'the whisperer who withdraws'. The word waswas is originally an infinitive in the sense of waswasah 'to whisper [ that is, to use breath instead of voice, when saying something in barely audible way ] '. But here it is used as an hyperbolic expression to refer to 'Shaitan' in the sense that 'he is an embodiment of whisper'. Whispering of the Shaitan means that he invites people to his obedience by a superstitious discourse in a way that its subject is cast into man's heart, but no voice is heard. [ Qurtubi ].

The word خَنَّاسِ khannas is derived from khanasa which means 'to sneak, recede or withdraw furtively'. The Shaitan is so named because he puts himself in a squatting [ perched ] position on the heart of man. So, when the latter becomes heedless, the former whispers, but when he remembers Allah, he withdraws furtively. When man becomes unmindful of Allah again, the Shaitan returns. Whenever man remembers Allah, he withdraws. This practice continues persistently. The Messenger of Allah ﷺ is reported to have said:

"Allah has built two houses in the heart of man, in one of which an angel resides and in the other the Shaitan. The angel urges him to do good works and the Shaitan induces him to do evil works. When man remembers Allah, the Shaitan withdraws. And when he stops remembering Allah, the Shaitan perches on the heart of man and pecks with his beak to whisper into it to do evil things." [ Transmitted by Abu Ya` la on the authority of Anas ؓ ، as quoted by Mazhari ].