Musnad Ahmad 944:18

Al-Hasan ibn Musa al-Ashyab narrated to us, Ibn Lahi'ah narrated to us, Abu al-Aswad narrated to us, that he heard 'Urwah narrating from 'Amarah ibn Khuzaymah al-Ansari, narrating from his father, that the Messenger of Allah, peace and blessings of Allah be upon him, said: "Satan comes to a person and says: 'Who created the heavens?' He says: 'Allah.' Then he says: 'Who created the earth?' He says: 'Allah.' Until he says: 'Who created Allah?' So if any of you finds that, let him say: 'I believe in Allah and His Messenger.'"