Satan

Never did We send a messenger or a prophet before thee, but, when he framed a desire, Satan threw some (vanity) into his desire: but Allah will cancel anything (vain) that Satan throws in, and Allah will confirm (and establish) His Signs: for Allah is full of Knowledge and Wisdom. (Quran 22:52)

That He may make the suggestions thrown in by Satan, but a trial for those in whose hearts is a disease and who are hardened of heart: verily the wrong-doers are in a schism far (from the Truth). (Quran 22:53)