Sunan Abi Dawud Book 15, Hadith 64
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.
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.
The Messenger of Allah (ﷺ) said: If anyone fights in Allah's path as long as the time between two milkings of a she-camel, Paradise will be assured for him. If anyone sincerely asks Allah for being killed and then dies or is killed, there will be a reward of a martyr for him. Ibn al-Musaffa added from here: If anyone is wounded in Allah's path, or suffers a misfortune, it will come on the Day of resurrection as copious as possible, its colour saffron, and its odour musk; and if anyone suffers from ulcers while in Allah's path, he will have on him the stamp of the martyrs.