Sahih Bukhari, Chapter: Funerals (Al-Janaaiz)

The Prophet collected every two martyrs of Uhud in one piece of cloth, then he would ask, "Which of them had (knew) more of the Quran?" When one of them was pointed out for him, he would put that one first in the grave and say, "I will be a witness on these on the Day of Resurrection." He ordered them to be buried with their blood on their bodies and they were neither washed nor was a funeral prayer offered for them.