It is narrated from Abu Muhriz (may Allah have mercy on him) that Sayyiduna Uthman bin Abi al-As (may Allah be pleased with him) came to the Messenger of Allah (peace and blessings be upon him) as part of a delegation with some people of Thaqif. When they were about to go in to the Prophet (peace and blessings be upon him), they said to him: Look after our belongings, or our mounts, for us. He (Sayyiduna Uthman bin Abi al-As (may Allah be pleased with him)) said: On the condition that when you set off, you wait for me until I come out from the Messenger of Allah (peace and blessings be upon him). Uthman (may Allah be pleased with him) says: "Then I went in to the Messenger of Allah (peace and blessings be upon him) and asked him for a mushaf that he had, and he gave it to me. He appointed me as governor over them (my people), and made me their imam, though I was the youngest of them."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8361