Sahih al-Bukhari 1346
Sahih al-Bukhari · Book 23: Funerals (Al-Janaa'iz) · Whoever thinks no bath is required for the martyrs
Narrated Jabir:
حَدَّثَنَا أَبُو الْوَلِيدِ ، حَدَّثَنَا لَيْثٌ ، عَنِ ابْنِ شِهَابٍ ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ كَعْبٍ ، عَنْ جَابِرٍ ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم " ادْفِنُوهُمْ فِي دِمَائِهِمْ ". ـ يَعْنِي يَوْمَ أُحُدٍ ـ وَلَمْ يُغَسِّلْهُمْ.
The Prophet (ﷺ) said, "Bury them (i.e. martyrs) with their blood." (that was) On the day of the Battle of Uhud. He did not get them washed.