Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
muslim:1628dZuhayr b. Ḥarb > al-Ḥasan b. Mūsá > Zuhayr > Simāk b. Ḥarb > Muṣʿab b. Saʿd from his father

Permit me to give away my property as I like. He refused. I (again) said: (Permit me) to give away half. He (again refused). I (again said): Then one-third. He (the Holy Prophet) observed silence after (I had asked permission to give away) one-third. He (the narrater) said: It was then that endowment of one-third became permissible.  

مسلم:١٦٢٨dوَحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ حَدَّثَنَا الْحَسَنُ بْنُ مُوسَى حَدَّثَنَا زُهَيْرٌ حَدَّثَنَا سِمَاكُ بْنُ حَرْبٍ حَدَّثَنِي مُصْعَبُ بْنُ سَعْدٍ عَنْ أَبِيهِ قَالَ

مَرِضْتُ فَأَرْسَلْتُ إِلَى النَّبِيِّ ﷺ فَقُلْتُ دَعْنِي أَقْسِمْ مَالِي حَيْثُ شِئْتُ فَأَبَى قُلْتُ فَالنِّصْفُ فَأَبَى قُلْتُ فَالثُّلُثُ قَالَ فَسَكَتَ بَعْدَ الثُّلُثِ قَالَ فَكَانَ بَعْدُ الثُّلُثُ جَائِزًا