ENOfficial
It was narrated from Ibraheem` bin `Abdullah bin Farrookh that his father said: I saw `Uthman bin `Affan (رضي الله عنه) buried in his clothes soaked with his blood. he was not washed.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا عَبْد اللَّهِ، حَدَّثَنِي سُرَيْجُ بْنُ يُونُسَ، حَدَّثَنَا مَحْبُوبُ بْنُ مُحْرِزٍ، عَنْ إِبْرَاهِيمَ بْنِ عَبْدِ اللَّهِ بْنِ فَرُّوخَ، عَنْ أَبِيهِ، قَالَ شَهِدْتُ عُثْمَانَ بْنَ عَفَّانَ رَضِيَ اللَّهُ عَنْهُ دُفِنَ فِي ثِيَابِهِ بِدِمَائِهِ وَلَمْ يُغَسَّلْ.
sunnah.com