Sahih Muslim 135 a
It is narrated on the authority of Abu Huraira that the Messenger of Allah (ﷺ) observed:
People will constantly ask you questions pertaining to knowledge till they would say: Allah created us, but who created Allah? he (the narrator) says: he (Abu Huraira) was (at the time of narrating this hadith) catching hold of the hand of a man and he said: Allah and the Messenger told the truth. Two persons have already put me this question, and this is the third one, or he said: One man has put me this question and he is the second one.
حَدَّثَنِي عَبْدُ الْوَارِثِ بْنُ عَبْدِ الصَّمَدِ، قَالَ حَدَّثَنِي أَبِي، عَنْ جَدِّي، عَنْ أَيُّوبَ، عَنْ مُحَمَّدِ بْنِ سِيرِينَ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏
"‏ لاَ يَزَالُ النَّاسُ يَسْأَلُونَكُمْ عَنِ الْعِلْمِ حَتَّى يَقُولُوا هَذَا اللَّهُ خَلَقَنَا فَمَنْ خَلَقَ اللَّهَ ‏"‏ ‏.‏ قَالَ وَهُوَ آخِذٌ بِيَدِ رَجُلٍ فَقَالَ صَدَقَ اللَّهُ وَرَسُولُهُ قَدْ سَأَلَنِي اثْنَانِ وَهَذَا الثَّالِثُ ‏.‏ أَوْ قَالَ سَأَلَنِي وَاحِدٌ وَهَذَا الثَّانِي ‏.‏