Sahih Bukhari Volume 007, Book 070, Hadith Number 572.
Narrated By Sad : Allah's Apostle came to visit me during my ailment which had been aggravated during Hajjat-al-Wada'. I said to him, "You see how sick I am. I have much property but have no heir except my only daughter May I give two thirds of my property in charity?"! He said, "No." I said, "Half of it?" He said, "No." I said "One third?" He said, "One third is too much, for to leave your heirs rich is better than to leave them poor, begging of others. Nothing you spend seeking Allah's pleasure but you shall get a reward for it, even for what you put in the mouth of your wife."