Sahih al-Bukhari 3051
Sahih al-Bukhari · Book 56: Fighting for the Cause of Allah (Jihaad) · If an infidel warrior comes in an Islamic territory
Narrated Salama bin Al-Akwa`:
حَدَّثَنَا أَبُو نُعَيْمٍ ، حَدَّثَنَا أَبُو الْعُمَيْسِ ، عَنْ إِيَاسِ بْنِ سَلَمَةَ بْنِ الأَكْوَعِ ، عَنْ أَبِيهِ ، قَالَ أَتَى النَّبِيَّ صلى الله عليه وسلم عَيْنٌ مِنَ الْمُشْرِكِينَ وَهْوَ فِي سَفَرٍ، فَجَلَسَ عِنْدَ أَصْحَابِهِ يَتَحَدَّثُ ثُمَّ انْفَتَلَ، فَقَالَ النَّبِيُّ صلى الله عليه وسلم " اطْلُبُوهُ وَاقْتُلُوهُ ". فَقَتَلَهُ فَنَفَّلَهُ سَلَبَهُ.
"An infidel spy came to the Prophet (ﷺ) while he was on a journey. The spy sat with the companions of the Prophet (ﷺ) and started talking and then went away. The Prophet (ﷺ) said (to his companions), 'Chase and kill him.' So, I killed him." The Prophet (ﷺ) then gave him the belongings of the killed spy (in addition to his share of the war booty).