Sunan Abi Dawud Book 15, Hadith 63
AbuSalam reported on the authority of a man from the companion of the Prophet (ﷺ). He said: We attacked a tribe of Juhaynah. A man from the Muslims pursued a man of them, and struck him but missed him. He struck himself with the sword. The Messenger of Allah (ﷺ) said: Your brother, O group of Muslims. The people hastened towards him, but found him dead. The Messenger of Allah (ﷺ) wrapped him with his clothes and his blood, and offered (funeral) prayer for him and buried him. They said: Messenger of Allah, is he a martyr? He said: Yes, and I am witness to him.
Salamah bin Al Akwa’ said “On the day of the battle of the Khaibar, my brother fought desperately. But his sword fell back on him and killed him. The Companions of the Apostle of Allaah(ﷺ) talked about him and doubted it (his martyrdom) saying “A man who died with his own weapon”. The Apostle of Allaah(ﷺ) said “he died as a warrior striving in the path of Allaah. Ibn Shihab said “I asked the son of Salamah bin Al Akwa’.” He narrated to me on the authority of his father similar to that except that he said “The Apostle of Allaah(ﷺ) said “They told a lie, he died as a warrior striving in the path of Allaah. There is a double reward for him.””
The Prophet (ﷺ) said: Two (prayers) are not rejected, or seldom rejected: Prayer at the time of the call to prayer, and (the prayer) at the time of fighting, when the people grapple with each other. Musa said: Rizq ibn Sa'id ibn AbdurRahman reported from AbuHazim on the authority of Sahl ibn Sa'd from the Prophet (ﷺ) as saying: And while it is raining.