It wasnarrated from Abu Sa'eed Al-Khudri that the Prophet (ﷺ)said:
"The one who fights in the cause of Allah has a guarantee fromAllah. Either He will raise him to His forgiveness and mercy, or Hewill send him back with reward and spoils of war. The likeness of theone who fights in the cause of Allah is that of one who fasts andprays at night without ceasing, until he returns."
English reference: Vol. 4, Book 24, Hadith 2754
Arabic reference: Book 24, Hadith 2859