Musnad Ahmad #515
Musnad Uthman ibn Affan
The Arabic includes the chain of narration (sanad) and the collector's commentary; the English translation shows the Prophet's words only.
حَدَّثَنَا حَسَنُ بْنُ مُوسَى، حَدَّثَنَا أَبُو هِلَالٍ، حَدَّثَنَا قَتَادَةُ، أَنَّ عُثْمَانَ، قُتِلَ وَهُوَ ابْنُ تِسْعِينَ سَنَةً أَوْ ثَمَانٍ وَثَمَانِينَ.
Qatadah narrated that `Uthman (رضي الله عنه) was killed when he was ninety years old or eighty-eight years old.
About Musnad Ahmad
This hadith is #515 from Musnad Ahmad, in the Book of Musnad Uthman ibn Affan.