The Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, said: "If someone is killed in the way of Allah سبحانه وتعالى while fighting in front of the Imam of the Muslims and dies immediately, he does not need to be washed. He is buried in the clothes he was killed in, except for his trousers, which are removed unless they have bloodstains, in which case they are buried with him. Likewise, any fur or cap he was wearing is removed unless stained with blood, in which case they are buried with him. However, his shoes are removed in all cases. If he does not die immediately but lives for some time and then dies later, he is washed, shrouded, perfumed, and buried properly. As for anyone else killed, whether justly or unjustly, they are to be washed, shrouded, perfumed, and buried."
Commentary #38