It was narrated that Abu Sa'eed Al-Khudri said:
"The Messenger of Allah said: 'Allah smiles at three things: a row in the prayer, a man who prays in the depths of the night, and a man who fights' I think he said, 'behind the battalion.'" (ID)
English reference (ID): Vol. 1, Book 1, Hadith 200 (ID)
Arabic reference (ID): Book 1, Hadith 205 (ID)