Sahih al-Bukhari, Hadith 4065

When it was the day of Uhud, the pagans were defeated. Then Satan, Allah's Curse be upon him, cried loudly, "O Allah's Worshippers, beware of what is behind!" On that, the front files of the (Muslim) forces turned their backs and started fighting with the back files. Hudhaifa looked, and on seeing his father Al-Yaman, he shouted, "O Allah's Worshippers, my father, my father!" But by Allah, they did not stop till they killed him. Hudhaifa said, "May Allah forgive you." (The sub-narrator, `Urwa, said, "By Allah, Hudhaifa continued asking Allah's Forgiveness for the killers of his father till he departed to Allah (i.e. died).")