Sahih Muslim 96 a
It is narrated on the authority of Usama b. Zaid that the Messenger of Allah (ﷺ) sent us in a raiding party. We raided Huraqat of Juhaina in the morning. I caught hold of a man and he said:
There is no god but Allah, I attacked him with a spear. It once occurred to me and I talked about it to the Apostle (ﷺ). The Messenger of Allah (ﷺ) said: Did he profess" There is no god but Allah," and even then you killed him? I said: Messenger of Allah, he made a profession of it out of the fear of the weapon. He (the Holy Prophet) observed: Did you tear his heart in order to find out whether it had professed or not? And he went on repeating it to me till I wished I had embraced Islam that day. Sa'd said: By Allah, I would never kill any Muslim so long as a person with a heavy belly, i. e., Usama, would not kill. Upon this a person remarked: Did Allah not say this: And fight them until there is no more mischief and religion is wholly for Allah? Sa'd said: We fought so that there should be no mischief, but you and your companions wish to fight so that there should be mischief.
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو خَالِدٍ الأَحْمَرُ، ح وَحَدَّثَنَا أَبُو كُرَيْبٍ، وَإِسْحَاقُ بْنُ إِبْرَاهِيمَ، عَنْ أَبِي مُعَاوِيَةَ، كِلاَهُمَا عَنِ الأَعْمَشِ، عَنْ أَبِي ظِبْيَانَ، عَنْ أُسَامَةَ بْنِ زَيْدٍ، وَهَذَا، حَدِيثُ ابْنِ أَبِي شَيْبَةَ قَالَ بَعَثَنَا رَسُولُ اللَّهِ صلى الله عليه وسلم فِي سَرِيَّةٍ فَصَبَّحْنَا الْحُرَقَاتِ مِنْ جُهَيْنَةَ فَأَدْرَكْتُ رَجُلاً فَقَالَ لاَ إِلَهَ إِلاَّ اللَّهُ ‏.‏ فَطَعَنْتُهُ فَوَقَعَ فِي نَفْسِي مِنْ ذَلِكَ فَذَكَرْتُهُ لِلنَّبِيِّ صلى الله عليه وسلم فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ أَقَالَ لاَ إِلَهَ إِلاَّ اللَّهُ وَقَتَلْتَهُ ‏"‏ ‏.‏ قَالَ قُلْتُ يَا رَسُولَ اللَّهِ إِنَّمَا قَالَهَا خَوْفًا مِنَ السِّلاَحِ ‏.‏ قَالَ ‏"‏ أَفَلاَ شَقَقْتَ عَنْ قَلْبِهِ حَتَّى تَعْلَمَ أَقَالَهَا أَمْ لاَ ‏"‏ ‏.‏ فَمَازَالَ يُكَرِّرُهَا عَلَىَّ حَتَّى تَمَنَّيْتُ أَنِّي أَسْلَمْتُ يَوْمَئِذٍ ‏.‏ قَالَ فَقَالَ سَعْدٌ وَأَنَا وَاللَّهِ لاَ أَقْتُلُ مُسْلِمًا حَتَّى يَقْتُلَهُ ذُو الْبُطَيْنِ ‏.‏ يَعْنِي أُسَامَةَ قَالَ قَالَ رَجُلٌ أَلَمْ يَقُلِ اللَّهُ ‏{‏ وَقَاتِلُوهُمْ حَتَّى لاَ تَكُونَ فِتْنَةٌ وَيَكُونَ الدِّينُ كُلُّهُ لِلَّهِ‏}‏ فَقَالَ سَعْدٌ قَدْ قَاتَلْنَا حَتَّى لاَ تَكُونَ فِتْنَةٌ وَأَنْتَ وَأَصْحَابُكَ تُرِيدُونَ أَنْ تُقَاتِلُوا حَتَّى تَكُونَ فِتْنَةٌ ‏.‏