It has been narrated on the authority of Abu Huraira (R.A) that the Messenger of Allah (peace be upon him) said:
God laughs at the two men both of whom will enter Paradise (though) one of them kills the other. They said: Messenger of Allah (peace be upon him), how is it? He said: One of them fights in the way of Allah, the Almighty and Exalted. and dies a martyr. Then God turns in mercy to the murderer who embraces Islam, fights in the way of Allah, the Almighty and Exalted, and dies a martyr.
Sahih Muslim, Book 33, Hadith 188
