The Book of Virtues
وَحَدَّثَنِي نَصْرُ بْنُ عَلِيٍّ، حَدَّثَنَا بِشْرٌ، - يَعْنِي ابْنَ مُفَضَّلٍ - حَدَّثَنَا خَالِدٌ الْحَذَّاءُ، حَدَّثَنَا عَمَّارٌ، مَوْلَى بَنِي هَاشِمٍ حَدَّثَنَا ابْنُ عَبَّاسٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم تُوُفِّيَ وَهُوَ ابْنُ خَمْسٍ وَسِتِّينَ .Ammar, the freed slave of Banu Hashim, reported that Ibn 'Abbas said that Allah's Messenger (ﷺ) died when he had attained the age of sixty-five
From Sahih Muslim, whose reports the scholars accept as authentic.