Chapter 30: The Book of Wills
It was narrated from 'Amr bin Shu' aib, from his father, from his grandfather, that a man came to the Prophet and said: "I am poor and I do not have anything, and I have an orphan (under my care)." He said: "Eat from the property of your orphan without being extravagant, wasteful or keeping it as capital for yourself."
Sunan an-Nasa'i 3668