Ibraaheem bin Adham stated:

It reached me that Umar bin Abd al-Azeez (rahimahullaah) stated to Khaalid bin …
Advice of Khaalid Bin Safwaan to Umar Bin Abd Al-Azeez That Made Him Cry
Learn Extra
http://piousmuslim.com/articles/bszmame-recommendation-of-khalid-bin-safwaan-to-umar-bin-abd-al-azeez-that-made-him-bawl.cfm