Musannaf Ibn Abi Shayba 27:800

Yahya ibn Abi Bukayr narrated to us, from Shu'bah, from Abdullah ibn 'Amr ibn Murrah, from 'Amr ibn Murrah, from Khaythamah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) was asked: "Which of the people are best?" He said: "The people of Yemen."