Musnad Ahmad 27:610

He said: I found in my father’s book: Yazid narrated to us, Shu’bah informed us, from ‘Abdullah ibn Dinar, from Ibn ‘Umar, who said: "The Messenger of Allah, may Allah bless him and grant him peace, appointed Dhu al-Hulayfah for the people of Medina, al-Juhfah for the people of Syria, and Qarn for the people of Najd." Ibn ‘Umar said: "And I was informed that he appointed Yalamlam for the people of Yemen."