The Messenger of Allah ﷺ said on the day of Uhud, "Wrap them in their clothes." He would bury several men together in a single grave, and he said, "Place the one who knew the most of the Quran at the front."
حدثنا هشيم عن محمد بن إسحاق عن الزهري
أن رسول الله ﷺ قال يوم أحد زملوهم في ثيابهم قال وجعل يدفن في القبر الرهط قال وقال قدموا أكثرهم قرآنا
No references are available.
Its isnad is sahih, and it is found in Nasai 4/78 no. 2002 in the chapter on funerals, Ibn Majah no. 2375, and Daraqutni 3/42.