Sahih Muslim 2658eBook 46, Hadith 37
حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا جَرِيرٌ، عَنِ الأَعْمَشِ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَا مِنْ مَوْلُودٍ إِلاَّ يُلِدَ عَلَى الْفِطْرَةِ فَأَبَوَاهُ يُهَوِّدَانِهِ وَيُنَصِّرَانِهِ وَيُشَرِّكَانِهِ " . فَقَالَ رَجُلٌ يَا رَسُولَ اللَّهِ أَرَأَيْتَ لَوْ مَاتَ قَبْلَ ذَلِكَ قَالَ " اللَّهُ أَعْلَمُ بِمَا كَانُوا عَامِلِينَ " .
No babe is born but upon Fitra. It is his parents who make him a Jew or a Christian or a Polytheist. A person said: Allah's Messenger, what is your opinion if they were to die before that (before reaching the age of adolescence when they can distinguish between right and wrong)? He said: It is Allah alone Who knows what they would be doing.