وعن البراء رضي الله عنه
قال أتى النبي صلى الله عليه وسلم رجل مقنع بالحديد، فقال: يا رسول الله أقاتل أو أسلم؟ قال: «أسلم، ثم قاتل«فأسلم، ثم قاتل فقتل، فقال رسول الله صلى الله عليه وسلم: عمل قليلا وأُجر كثيرًا»
A man equipped with arms came to the Prophet (sallallahu alayhi wa sallam) and asked: “O Messenger of Allah! Should I go and fight or should I embrace Islam first?” He (sallallahu alayhi wa sallam) replied, “Enter in the fold of Islam and then fight.” He embraced Islam and fought until he was killed. Thereupon the Messenger of Allah (sallallahu alayhi wa sallam) said, “He accepted Islam for a short time but was rewarded much.”.
Riyad as-Salihin 1310, Book 12, The Book of Jihad, Hadith 26. 1 min read