Chapter 30: The Book of Wills
' Amir bin Sa' d (narrated) from his father that he fell sick in Makkah and the Messenger of Allah came to him. When Sa' d saw him, he wept and said: "O Messenger of Allah, am I to die in the land from which I emigrated?" He said: "No, if Allah wills." He said: "O Messenger of Allah, shall I bequeath all of my wealth in the cause of Allah?" He said: "No." He said: "Two-thirds?" He said: "No." He said: "Half of it?" He said: "No." He said: "One-third of it?" The Messenger of Allah said: "One-third, and one-third is a lot. If you leave your sons independent of means that is better than if you leave them poor, holding out their hands to people."
Sunan an-Nasa'i 3630