It is narrated from Harithah bin Mudarrib that Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) wrote to us: "I am sending to you Ammar bin Yasir as governor, and Abdullah bin Mas'ud as teacher and minister. These two are among the distinguished Companions of Muhammad (peace and blessings be upon him) and among the people of Badr, so listen to them. I have appointed Ibn Mas'ud over your treasury (Bayt al-Mal), so listen to them, learn from them and follow them. And indeed I have preferred you over myself in the matter of Abdullah (bin Mas'ud) (by sending him to you instead of keeping him with me)." This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), and they did not record it.