Musannaf Ibn Abi Shayba 27:807

Shababa narrated to us, he said: Shu'bah narrated to us, from Salamah ibn Kuhayl, from Habbah al-'Arani, that 'Umar ibn al-Khattab said: "O people of Kufa, you are the head of the Arabs and their skull, and my arrow with which I shoot if something comes to me from here and from there. And I have sent to you 'Abdullah ibn Mas'ud, and I have chosen him for you, and I have preferred you with him over my own self."