Sahih Bukhari Volume 5, Book 64, Hadith 4209

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ، حَدَّثَنَا ابْنُ أَبِي حَازِمٍ، عَنْ أَبِيهِ، عَنْ سَهْلٍ، قَالَ الْتَقَى النَّبِيُّ صلى الله عليه وسلم وَالْمُشْرِكُونَ فِي بَعْضِ مَغَازِيهِ فَاقْتَتَلُوا، فَمَالَ كُلُّ قَوْمٍ إِلَى عَسْكَرِهِمْ، وَفِي الْمُسْلِمِينَ رَجُلٌ لاَ يَدَعُ مِنَ الْمُشْرِكِينَ شَاذَّةً وَلاَ فَاذَّةً إِلاَّ اتَّبَعَهَا فَضَرَبَهَا بِسَيْفِهِ، فَقِيلَ يَا رَسُولَ اللَّهِ مَا أَجْزَأَ أَحَدُهُمْ مَا أَجْزَأَ فُلاَنٌ‏.‏ فَقَالَ ‏"‏ إِنَّهُ مِنْ أَهْلِ النَّارِ ‏"‏‏.‏ فَقَالُوا أَيُّنَا مِنْ أَهْلِ الْجَنَّةِ إِنْ كَانَ هَذَا مِنْ أَهْلِ النَّارِ فَقَالَ رَجُلٌ مِنَ الْقَوْمِ لأَتَّبِعَنَّهُ، فَإِذَا أَسْرَعَ وَأَبْطَأَ كُنْتُ مَعَهُ‏.‏ حَتَّى جُرِحَ فَاسْتَعْجَلَ الْمَوْتَ، فَوَضَعَ نِصَابَ سَيْفِهِ بِالأَرْضِ، وَذُبَابَهُ بَيْنَ ثَدْيَيْهِ، ثُمَّ تَحَامَلَ عَلَيْهِ، فَقَتَلَ نَفْسَهُ، فَجَاءَ الرَّجُلُ إِلَى النَّبِيِّ صلى الله عليه وسلم فَقَالَ أَشْهَدُ أَنَّكَ رَسُولُ اللَّهِ فَقَالَ ‏"‏ وَمَا ذَاكَ ‏"‏‏.‏ فَأَخْبَرَهُ‏.‏ فَقَالَ ‏"‏ إِنَّ الرَّجُلَ لَيَعْمَلُ بِعَمَلِ أَهْلِ الْجَنَّةِ، فِيمَا يَبْدُو لِلنَّاسِ، وَإِنَّهُ مِنْ أَهْلِ النَّارِ، وَيَعْمَلُ بِعَمَلِ أَهْلِ النَّارِ، فِيمَا يَبْدُو لِلنَّاسِ وَهْوَ مِنْ أَهْلِ الْجَنَّةِ ‏"

Narrated By Sahl : During one of his Ghazawat, the Prophet encountered the pagans, and the two armies fought, and then each of them returned to their army camps. Amongst the (army of the) Muslims there was a man who would follow every pagan separated from the army and strike him with his sword. It was said, "O Allah's Apostle! None has fought so satisfactorily as so-and-so (namely, that brave Muslim). "The Prophet said, "He is from the dwellers of the Hell-Fire." The people said, "Who amongst us will be of the dwellers of Paradise if this (man) is from the dwellers of the Hell-Fire?" Then a man from amongst the people said, "I will follow him and accompany him in his fast and slow movements." The (brave) man got wounded, and wanting to die at once, he put the handle of his sword on the ground and its tip in between his breasts, and then threw himself over it, committing suicide. Then the man (who had watched the deceased) returned to the Prophet and said, "I testify that you are Apostle of Allah." The Prophet said, "What is this?" The man told him the whole story. The Prophet said, "A man may do what may seem to the people as the deeds of the dwellers of Paradise, but he is of the dwellers of the Hell-Fire and a man may do what may seem to the people as the deeds of the dwellers of the Hell-Fire, but he is from the dwellers of Paradise."