Sayyiduna Abu Hurairah (may Allah be pleased with him) narrated that the Messenger of Allah (peace and blessings be upon him) said: Satan comes to one of you and raises questions in your heart, first asking, "Who created such and such? Who created such and such?" until he finally says, "Who created your Lord?" When anyone experiences such a whisper, he should seek refuge with Allah and abandon that satanic thought.

Sayyiduna Anas bin Malik (may Allah be pleased with him) narrated that the Messenger of Allah (peace and blessings of Allah be upon him) said: A person will continue to ask questions until he will ask: "This is Allah, the Creator of everything, but who created Allah?" (God forbid, Satan will cast this doubt into their hearts).