صَحِيحُ مُسْلِمٍ
Sahih Muslim 134 a
The Book of Faith
Clarifying the Waswasah (Whispers, Bad Thoughts) with regard to faith, and what the one who experiences that should say
حَدَّثَنَا هَارُونُ بْنُ مَعْرُوفٍ، وَمُحَمَّدُ بْنُ عَبَّادٍ، - وَاللَّفْظُ لِهَارُونَ - قَالاَ حَدَّثَنَا سُفْيَانُ، عَنْ هِشَامٍ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم لاَ يَزَالُ النَّاسُ يَتَسَاءَلُونَ حَتَّى يُقَالَ هَذَا خَلَقَ اللَّهُ الْخَلْقَ فَمَنْ خَلَقَ اللَّهَ فَمَنْ وَجَدَ مِنْ ذَلِكَ شَيْئًا فَلْيَقُلْ آمَنْتُ بِاللَّهِ .
It is narrated on the authority of Abu Huraira that the Messenger of Allah (ﷺ) said: Men will continue to question one another till this is propounded: Allah created all things but who created Allah? He who found himself confronted with such a situation should say: I affirm my faith in Allah.
Sahih Muslim, 134 aSahihصحيح