The specific procedure jurists describe for ghusl al-mayyit traces closely to a hadith reporting instructions Muhammad gave to the women washing his own daughter's body, telling them to wash her an odd number of times, three or five or more if they judged it needed, using water and the leaves of the lote tree, and to add a trace of camphor on the final washing, a report that supplies both the odd number rule and the camphor still used today directly from a named, remembered event rather than from abstract legal reasoning.
Not every body that would ordinarily receive this washing is washed at all: classical law makes a specific exception for those killed in battle for the faith, martyrs, who are traditionally buried in the clothing and blood they died in rather than washed and shrouded in the usual manner, a status jurists tie to hadith describing Muhammad instructing that the dead of a particular battle be buried as they were rather than prepared in the ordinary way. That exception marks martyrdom as carrying its own distinct legal category within Islamic funeral law, one of the few circumstances in which the otherwise near universal obligation to wash a deceased Muslim before burial does not apply, and jurists have historically debated at the margins exactly which deaths qualify for this treatment.