Sahih Bukhari
Beginning of Creation
Volume: 004 / Book Number: 054 / Hadith Number: 496
Narrated Abu Huraira:
Allah's Apostle said, "Satan comes to one of you and says, 'Who created so-and-so? 'till he says, 'Who has created your Lord?' So, when he inspires such a question, one should seek refuge with Allah and give up such thoughts."