Sunan Ibn Majah 218

It was narrated that Nafi' bin 'Abdul-Harith met 'Umar bin Khattab in 'Usfan, when 'Umar had appointed him as his governer in Makkah.:'Umar asked: "Whom have you appointed as your deputy over the people of the valley?" He said: "I have appointed Ibn Abza over them." 'Umar said: "Who is Ibn Abza?" Nafi' said: "One of our freed slaves." 'Umar said: "Have you appointed a freed slave over them?" Nafi' said: "He has great knowledge of the Book of Allah, is well versed in the rules of inheritance (Fara'id) and is a (good) judge." 'Umar said: "Did not your prophet say: 'Allah raises some people (in status) because of this book and brings others low because of it?