The Messenger of Allah ﷺ said, "Every newborn is born upon the natural disposition. It is his parents who make him a Jew or a Christian, just as animals produce their young whole. Do you find any of them mutilated before you yourselves mutilate them?"They asked, "Messenger of Allah, what about one who dies while still young?"He replied, "Allah knows best what they would have done."
قال رسول الله ﷺ: ما من مولود إلا يولد على الفطرة فأبواه يهودانه وينصرانه كما تنتجون البهيمة هل تجدون فيها من جدعاء حتى تكونوا أنتم تجدعونها قالوا: يا رسول الله أفرأيت من يموت وهو صغير قال: الله أعلم بما كانوا عاملين.
Bukhari related it in the Book of Qadar (6599), and Muslim in the Book of Qadar (2658:24), both through the route of Abdul-Razzaq, who said, Mamar informed us, from Hammam, from Abu Hurairah, who mentioned it.