Jami` at-Tirmidhi Book 10, Hadith 73
Ash-Sha'bi said: "I was informed by one who saw the Prophet: He (pbuh) saw a solitary grave, s he lined his Companions (behind him) to pray over it." It was said to him (Ash-Sha'bi): "Who informed you?" He said: "Ibn Abbas."
Jabir bin Abdullah informed him that the Prophet had put two men together in one cloth from those who were killed at (the battle of) Uhud, then he said: "Which of them memorized the more of the Qur'an?" When one of them was indicated to him, he put him in the Lahd (first) and said: "I am a witness for those people on the Day of Judgment." And he ordered that they be buried in their blood, and that they not be prayed over, nor washed.
"Umm Sa'd died while the Prophet was absent. So when he arrived he performed Salat over her, and a month had already passed."