Sahih Muslim
The Book of Jihad and Expeditions — Hadith #4554
Scholarly Consensus: Sahih How we grade
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَإِسْحَاقُ بْنُ إِبْرَاهِيمَ، كِلاَهُمَا عَنْ حَاتِمِ بْنِ إِسْمَاعِيلَ، عَنْ جَعْفَرِ بْنِ مُحَمَّدٍ، عَنْ أَبِيهِ، عَنْ يَزِيدَ بْنِ هُرْمُزَ، أَنَّ نَجْدَةَ، كَتَبَ إِلَى ابْنِ عَبَّاسٍ يَسْأَلُهُ عَنْ خِلاَلٍ، . بِمِثْلِ حَدِيثِ سُلَيْمَانَ بْنِ بِلاَلٍ غَيْرَ أَنَّ فِي، حَدِيثِ حَاتِمٍ وَإِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم لَمْ يَكُنْ يَقْتُلُ الصِّبْيَانَ فَلاَ تَقْتُلِ الصِّبْيَانَ إِلاَّ أَنْ تَكُونَ تَعْلَمُ مَا عَلِمَ الْخَضِرُ مِنَ الصَّبِيِّ الَّذِي قَتَلَ . وَزَادَ إِسْحَاقُ فِي حَدِيثِهِ عَنْ حَاتِمٍ وَتُمَيِّزَ الْمُؤْمِنَ فَتَقْتُلَ الْكَافِرَ وَتَدَعَ الْمُؤْمِنَ .
The Messenger of Allah (ﷺ) used not to kill the children, so thou shouldst not kill them unless you could know what Khadir had known about the child he killed, or you could distinguish between a child who would grow up to he a believer (and a child who would grow up to be a non-believer), so that you killed the (prospective) non-believer and left the (prospective) believer aside.
Hadith Grading
Each grade below reflects one scholar's assessment of the chain of transmission. The grade describes the chain, not the Prophet's words. How we grade
Scholarly Consensus: Sahih