The Messenger of Allah ﷺ said, "Every child is born upon the natural disposition. It is his parents who make him a Jew, a Christian, or a Zoroastrian, just as an animal gives birth to a whole, unblemished offspring. Do you find any of them mutilated at birth?"Then Abu Hurairah would say, "Recite if you wish, 'So direct your face toward the religion, inclining to truth. Adhere to the natural disposition of Allah upon which He has created all people. There is no altering Allah's creation. That is the upright religion, but most people do not know'" [Rum 30:30].
قال رسول الله ﷺ: ما من مولود إلا يولد على الفطرة، فأبواه يهودانه وينصرانه ويمجسانه، كما تنتج البهيمة بهيمة جمعاء، هل تحسون فيها من جدعاء؟ ثم يقول أبو هريرة: واقرؤا إن شئتم: {فأقم وجهك للدين حنيفا فطرت الله التي فطر الناس عليها لا تبديل لخلق الله ذلك الدين القيم ولكن أكثر الناس لا يعلمون} [الروم: ٣٠].
Bukhari narrated it in the Book of Funerals (1359), and Muslim in the Book of Divine Decree (2658), both from the hadith of Yunus bin Yazid, from Ibn Shihab, that Abu Salama bin Abdul-Rahman informed him, that Abu Hurairah said (and he mentioned it).