The Book of Wills
وَحَدَّثَنِي الْقَاسِمُ بْنُ زَكَرِيَّاءَ، حَدَّثَنَا حُسَيْنُ بْنُ عَلِيٍّ، عَنْ زَائِدَةَ، عَنْ عَبْدِ الْمَلِكِ، بْنِ عُمَيْرٍ عَنْ مُصْعَبِ بْنِ سَعْدٍ، عَنْ أَبِيهِ، قَالَ عَادَنِي النَّبِيُّ صلى الله عليه وسلم فَقُلْتُ أُوصِي بِمَالِي كُلِّهِ . قَالَ " لاَ " . قُلْتُ فَالنِّصْفُ . قَالَ " لاَ " . فَقُلْتُ أَبِالثُّلُثِ فَقَالَ " نَعَمْ وَالثُّلُثُ كَثِيرٌ " .Ibn Sa'd reported his father as saying:Allah's Apostle (ﷺ) visited me during my illness. I said: I am willing away the whole of my property. He said: No. I said: Then half? He said: No. I said: Should I will away one-third? He said: Yes, and even one-third is enough
From Sahih Muslim, whose reports the scholars accept as authentic.