Sahih Bukhari, Chapter: Funerals (Al-Janaaiz)

Allah's Apostle shrouded every two martyrs of Uhud in one piece of cloth and then he would ask, "Which of them knew more Quran?" When one of them was pointed out he would put him first in the grave. He said, "I am a witness on these." Then he ordered them to be buried with blood on their bodies. Neither did he offer their funeral prayer nor did he get them washed. (Jabir bin Abdullah added): Allah's Apostle used to ask about the martyrs of Uhud as to which of them knew more of the Quran." And when one of them was pointed out as having more of it he would put him first in the grave and then his companions. (Jabir added): My father and my uncle were shrouded in one sheet.