Hadith 6599, 6600 - Divine Will (Al-Qadar) - Sahih Al-Bukhari - صحيح البخاري - Collection of Actions, Sayings and Teachings of Prophet Muhammad (صلى الله عليه و سلم) - Kutub as-Sittah

82. Divine Will (Al-Qadar) - كتاب القدر

3) Chapter: It is Allah Who knows what they would have done

Narrated Abu Huraira:

Allah's Messenger (ﷺ) said, "No child is born but has the Islamic Faith, but its parents turn it into a Jew or a Christian. It is as you help the animals give birth. Do you find among their offspring a mutilated one before you mutilate them yourself?" The people said, "O Allah's Messenger (ﷺ)! What do you think about those (of them) who die young?" The Prophet (ﷺ) said, "Allah knows what they would have done (were they to live)."

Reference: 6599, 6600
English reference: Vol. 8, Book 77, Hadith 597
In-book reference: Book 82, Hadith 6
Grade: Sahih
Read this hadith from Darussalam Collection

3) باب اللَّهُ أَعْلَمُ بِمَا كَانُوا عَامِلِينَ

حَدَّثَنِي إِسْحَاقُ، أَخْبَرَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنْ هَمَّامٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏‏‏.‏ قَالُوا يَا رَسُولَ اللَّهِ أَفَرَأَيْتَ مَنْ يَمُوتُ وَهْوَ صَغِيرٌ قَالَ ‏{‏اللَّهُ أَعْلَمُ بِمَا كَانُوا عَامِلِينَ‏}‏ "‏ مَا مِنْ مَوْلُودٍ إِلاَّ يُولَدُ عَلَى الْفِطْرَةِ، فَأَبَوَاهُ يُهَوِّدَانِهِ وَيُنَصِّرَانِهِ، كَمَا تُنْتِجُونَ الْبَهِيمَةَ، هَلْ تَجِدُونَ فِيهَا مِنْ جَدْعَاءَ حَتَّى تَكُونُوا أَنْتُمْ تَجْدَعُونَهَا ‏"