Jabir bin Abdullah reported,

The Prophet ﷺ used to wrap two of the slain at Uhud together in a single cloth, then he would ask, "Which of them had memorized more of the Quran?" When one of them was pointed out, he would place him first in the grave and say, "I will be a witness over these on the Day of Resurrection."He ordered that they be buried in their blood, without being washed, and no funeral prayer was performed over them.

Azami 3755

Sahih

عن جابر بن عبد الله قال

كان النبي ﷺ يجمع بين الرجلين من قتلى أحد في ثوب واحد، ثم يقول: أيهم أكثر أخذا للقرآن؟ فإذا أشير إلى أحدهما قدمه في اللحد وقال: أنا شهيد على هؤلاء يوم القيامة، وأمر بدفنهم في دمائهم، ولم يغسلوا، ولم يصل عليهم.

الأعظمي 3755صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Funerals
Chapter
Washing the martyrs, praying over them, and burying them
Section
Martyr in the cause of Allah is not washed, his clothes in which he was martyred are not removed, and the funeral prayer is not offered for him
Numbering
Jami al-Kamil 3755 (2nd edition)
Azami 3755