Mishkat al-Masabih 3858
Fadala b. ‘Ubaid told of hearing ‘Umar b. al-Khattab say he had heard God’s Messenger saying, "The martyrs are of four types:
(1) a believing man whose faith is good who meets the enemy and is sincere towards God till he is killed, and that is the one to whom men will raise their eyes on the day of resurrection thus (raising his head till his cap fell off, but I do not know whether he meant ‘Umar’s cap or the Prophet’s cap); (2) a believing man whose faith is good, who meets the enemy and appears as if his skin had been torn by acacia thorns through cowardice, and then is killed by a random arrow, he being in the second class; (3) a believing man who mingles a good deed with another which is bad who meets the enemy and is sincere towards God till he is killed, that one being in the third class; (4) a believing man who has been dissipated who meets the enemy and is sincere towards God till he is killed, that one being in the fourth class.” 

Tirmidhi transmitted it, saying this is hasan gharib tradition.
وَعَن فَضالةَ بنِ عُبيد قَالَ: سمِعْتُ عمَرَ بن الْخطاب يَقُولُ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: 
" الشُّهَدَاءُ أَرْبَعَةٌ: رَجُلٌ مُؤْمِنٌ جَيِّدُ الْإِيمَانِ لَقِيَ الْعَدُوَّ فَصَدَقَ اللَّهَ حَتَّى قُتِلَ فَذَلِكَ الَّذِي يَرْفَعُ النَّاسُ إِلَيْهِ أَعْيُنَهُمْ يَوْمَ الْقِيَامَةِ هَكَذَا " وَرَفَعَ رَأْسَهُ حَتَّى سَقَطَتْ قَلَنْسُوَتُهُ فَمَا أَدْرِي أَقَلَنْسُوَةَ عُمَرَ أَرَادَ أَمْ قَلَنْسُوَةَ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ؟ قَالَ: «وَرَجُلٌ مُؤْمِنٌ جَيِّدُ الْإِيمَانِ لَقِيَ الْعَدُوَّ كَأَنَّمَا ضَرَبَ جِلْدَهُ بِشَوْكٍ طَلْحٍ مِنَ الْجُبْنِ أَتَاهُ سَهْمٌ غَرْبٌ فَقَتَلَهُ فَهُوَ فِي الدَّرَجَةِ الثَّانِيَةِ وَرَجُلٌ مُؤْمِنٌ خَلَطَ عَمَلًا صَالِحًا وَآخَرَ سَيِّئًا لَقِيَ الْعَدُوَّ فَصَدَقَ اللَّهَ حَتَّى قُتِلَ فَذَلِكَ فِي الدَّرَجَةِ الثَّالِثَةِ وَرَجُلٌ مُؤْمِنٌ أَسْرَفَ عَلَى نَفْسِهِ لَقِيَ الْعَدُوَّ فَصَدَقَ اللَّهَ حَتَّى قُتِلَ فَذَاكَ فِي الدَّرَجَةِ الرَّابِعَةِ» . رَوَاهُ التِّرْمِذِيُّ وَقَالَ: هَذَا حَدِيثٌ حَسَنٌ غَرِيبٌ