Musnad Abu Ya'la al-Mawsili 108:168

Abu Bakr narrated to us, Yahya ibn Adam narrated to us, from Abu al-Ahwas, from al-A'mash, from Abu Sufyan, from Jabir, who said: I heard the Messenger of Allah (peace be upon him) saying: "Faith is among the people of the Hijaz. And harshness and hardness of hearts are toward the East, in Rabi'ah and Mudar."