It is narrated from Sayyiduna Abu Huraira (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Allah will smile on the Day of Resurrection at two persons, both of whom will enter Paradise, though one killed the other. One person fought in the way of Allah and was killed, then Allah had mercy on his killer, and he became a Muslim, fought in jihad, and was martyred."