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كتاب الجهاد والسير
56  
Fighting for the Cause of Allah (Jihaad)
(28)
Chapter: A disbeliever kills a Muslim and later on embraces Islam
(28)
باب الْكَافِرِ يَقْتُلُ الْمُسْلِمَ ثُمَّ يُسْلِمُ فَيُسَدِّدُ بَعْدُ وَيُقْتَلُ
Sahih al-Bukhari 2827

Narrated Abu Huraira:

I went to Allah's Messenger (ﷺ) while he was at Khaibar after it had fallen in the Muslims' hands. I said, "O Allah's Messenger (ﷺ)! Give me a share (from the land of Khaibar)."

One of the sons of Sa'id bin Al-'As said, "O Allah's Messenger (ﷺ)! Do not give him a share." I said, "This is the murderer of Ibn Qauqal." The son of Said bin Al-As said, "Strange! A Wabr (i.e. guinea pig) who has come down to us from the mountain of Qaduim (i.e. grazing place of sheep) blames me for killing a Muslim who was given superiority by Allah because of me, and Allah did not disgrace me at his hands (i.e. was not killed as an infidel)." (The sub-narrator said "I do not know whether the Prophet (ﷺ) gave him a share or not.")

حَدَّثَنَا الْحُمَيْدِيُّ، حَدَّثَنَا سُفْيَانُ، حَدَّثَنَا الزُّهْرِيُّ، قَالَ أَخْبَرَنِي عَنْبَسَةُ بْنُ سَعِيدٍ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ قَالَ أَتَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم وَهْوَ بِخَيْبَرَ بَعْدَ مَا افْتَتَحُوهَا، فَقُلْتُ يَا رَسُولَ اللَّهِ أَسْهِمْ لِي‏.‏ فَقَالَ بَعْضُ بَنِي سَعِيدِ بْنِ الْعَاصِ لاَ تُسْهِمْ لَهُ يَا رَسُولَ اللَّهِ‏.‏ فَقَالَ أَبُو هُرَيْرَةَ هَذَا قَاتِلُ ابْنِ قَوْقَلٍ‏.‏ فَقَالَ ابْنُ سَعِيدِ بْنِ الْعَاصِ وَاعَجَبًا لِوَبْرٍ تَدَلَّى عَلَيْنَا مِنْ قَدُومِ ضَأْنٍ، يَنْعَى عَلَىَّ قَتْلَ رَجُلٍ مُسْلِمٍ أَكْرَمَهُ اللَّهُ عَلَى يَدَىَّ وَلَمْ يُهِنِّي عَلَى يَدَيْهِ‏.‏ قَالَ فَلاَ أَدْرِي أَسْهَمَ لَهُ أَمْ لَمْ يُسْهِمْ لَهُ‏.‏ قَالَ سُفْيَانُ وَحَدَّثَنِيهِ السَّعِيدِيُّ عَنْ جَدِّهِ عَنْ أَبِي هُرَيْرَةَ‏.‏ قَالَ أَبُو عَبْدِ اللَّهِ السَّعِيدِيُّ عَمْرُو بْنُ يَحْيَى بْنِ سَعِيدِ بْنِ عَمْرِو بْنِ سَعِيدِ بْنِ الْعَاصِ‏.‏
Reference : Sahih al-Bukhari 2827
In-book reference : Book 56, Hadith 43
USC-MSA web (English) reference : Vol. 4, Book 52, Hadith 80
  (deprecated numbering scheme)