Sunan Ibn Majah

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?