Sahih Bukhari Volume 4, Book 51, Hadith Number 7.
Narated By Sad : I fell sick and the Prophet paid me a visit. I said to him, “O Allah’s Apostle! I invoke Allah that He may not let me expire in the land whence I migrated (i.e. Mecca).” He said, “May Allah give you health and let the people benefit by you.” I said, “I want to will my property, and I have only one daughter and I want to will half of my property (to be given in charity).” He said,” Half is too much.” I said, “Then I will one third.” He said, “One-third, yet even one-third is too much.” (The narrator added, “So the people started to will one third of their property and that was Permitted for them.”)