Musnad Abu Ya'la al-Mawsili 2:113

Ahmad ibn Ibrahim al-Nukri Abu Abd Allah narrated to us, Abu Abd al-Rahman narrated to us, Ibn Lahi'ah narrated to us, 'Ata' ibn Dinar al-Hudhali informed me that Abu Yazid al-Khawlani narrated to him that he heard Fudalah ibn 'Ubayd say: I heard 'Umar ibn al-Khattab reporting from the Messenger of Allah (may Allah bless him and grant him peace) saying: "The martyrs are four: A man who is a believer, good in faith, who met the enemy and was truthful to Allah until he was killed; that is the one to whom people will raise their eyes on the Day of Resurrection like this," and he raised his head until his cap fell off—and I do not know if it was the cap of 'Umar or the cap of the Prophet (may Allah bless him and grant him peace). "And a man who is a believer, good in faith, until when he met the enemy, it was as if his skin was being struck by the thorns of the acacia tree out of cowardice, then a stray arrow came to him and killed him; he is in the second rank. "And a man who is a believer who mixed a righteous deed with another that was evil; he met the enemy and was truthful to Allah until he was killed; that is in the third rank. "And a man who is a believer who transgressed against his own soul; he met the enemy and was truthful to Allah until he was killed; that is in the fourth rank."