Hadithcore
Sahih Muslim, 1628 f
sahih

Ibn Sa'd reported his father as saying:

Allah's Messenger (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.

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 ‏"‏ ‏.‏

References2 variants
In-Book Reference
Book 25, Hadith 11
USC-MSA web (English) reference
Book 13, Hadith 3996 (deprecated numbering scheme)