Hadith 21:195
It was narrated from Sa'eed bin Hisham bin 'Amir that his father said:
"On the day of Uhud some of the people among the Muslims were killed, and people were wounded. The Messenger of Allah said: 'Dig graves and make them wide, and bury two or three in a grave, and put the one who knew more Qur'an in first."'
أَخْبَرَنَا مُحَمَّدُ بْنُ مَعْمَرٍ، قَالَ حَدَّثَنَا وَهْبُ بْنُ جَرِيرٍ، قَالَ حَدَّثَنَا أَبِي قَالَ، سَمِعْتُ حُمَيْدَ بْنَ هِلاَلٍ، عَنْ سَعْدِ بْنِ هِشَامِ بْنِ عَامِرٍ، عَنْ أَبِيهِ، قَالَ : لَمَّا كَانَ يَوْمُ أُحُدٍ أُصِيبَ مِنَ الْمُسْلِمِينَ، وَأَصَابَ النَّاسَ جِرَاحَاتٌ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم : " احْفِرُوا وَأَوْسِعُوا، وَادْفِنُوا الاِثْنَيْنِ وَالثَّلاَثَةَ فِي الْقَبْرِ، وَقَدِّمُوا أَكْثَرَهُمْ قُرْآنًا "
Original Reference: Sunan an-Nasa'i 2011