Anas reported God’s messenger as saying, “Men will continue to question one another till they propound this: ‘God created everything, but who created God?’ ” Bukhari transmitted it. Muslim’s version is: He declared that God said, “Your people will continue to ask, ‘What is this?’ and ‘what is that?’ till they propound this: God created all things, but who created God?”
Hadith Referenceمشكوة المصابيح / كتاب الإيمان / 76
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:متفق عليه
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «متفق عليه، رواه البخاري (7296) و مسلم (217 / 136)»