عَنْ عُمَارَةَ بْنِ خُزَيْمَةَ رَضِيَ اللَّهُ عَنْهُ يُحَدِّثُ عَنْ أَبِيهِ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ يَأْتِي الشَّيْطَانُ الْإِنْسَانَ فَيَقُولُ مَنْ خَلَقَ السَّمَاوَاتِ فَيَقُولُ اللَّهُ ثُمَّ يَقُولُ مَنْ خَلَقَ الْأَرْضَ فَيَقُولُ اللَّهُ حَتَّى يَقُولُ مَنْ خَلَقَ اللَّهَ فَإِذَا وَجَدَ أَحَدُكُمْ ذَلِكَ فَلْيَقُلْ آمَنْتُ بِاللَّهِ وَرَسُولِهِ
It is narrated from Sayyiduna Khuzaymah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: Satan comes to a person and says: Who created the heavens? He replies: Allah Almighty did. Then he asks: Who created the earth? He replies: Allah Almighty did. (This series of questions continues) until he says: Who created Allah? When anyone feels this, he should say: "Aamantu billahi wa rasoolihi" (I believe in Allah and His Messenger).