Sahih Muslim 95
Sahih Muslim · Book 1: The Book of Faith · The prohibition of killing a disbeliever after he says La ilaha illallah
It is narrated by Miqdad, and he was an ally of B. Zuhra and was of those who participated in the Battle of Badr along with the Messenger of Allah, that he said:
وَحَدَّثَنِي حَرْمَلَةُ بْنُ يَحْيَى ، أَخْبَرَنَا ابْنُ وَهْبٍ ، قَالَ أَخْبَرَنِي يُونُسُ ، عَنِ ابْنِ شِهَابٍ ، قَالَ حَدَّثَنِي عَطَاءُ بْنُ يَزِيدَ اللَّيْثِيُّ، ثُمَّ الْجُنْدَعِيُّ أَنَّ عُبَيْدَ، اللَّهِ بْنَ عَدِيِّ بْنِ الْخِيَارِ أَخْبَرَهُ أَنَّ الْمِقْدَادَ بْنَ عَمْرِو بْنِ الأَسْوَدِ الْكِنْدِيَّ - وَكَانَ حَلِيفًا لِبَنِي زُهْرَةَ وَكَانَ مِمَّنْ شَهِدَ بَدْرًا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم - أَنَّهُ قَالَ يَا رَسُولَ اللَّهِ أَرَأَيْتَ إِنْ لَقِيتُ رَجُلاً مِنَ الْكُفَّارِ ثُمَّ ذَكَرَ بِمِثْلِ حَدِيثِ اللَّيْثِ .
Messenger of Allah, here is a point: If I happened to encounter a person amongst the infidels (in the battle). Then he narrated a hadith similar to the one transmitted by Laith.