Sahih Muslim Book 33, Hadith Number 6432.

Chapter : Everyone is born according to his true nature and the command pertaining to the demise of the children of the infidels and of the children of the Muslims.

Abu Huraira reported that Allah’s Messenger (way peace be upon him) was asked about the children of the polytheists who die young. Thereupon Allah’s Apostle (may peace be upon him) said: It is Allah Who knows what they would be doing.