Musannaf Ibn Abi Shayba 27:794

Abu Mu'awiyah narrated to us, from al-A'mash, from Abu Salih, from Abu Hurayrah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "The people of Yemen have come to you; they are the softest of hearts and the most tender of inner selves. Faith is Yemeni, and wisdom is Yemeni. And the head of disbelief is toward the east."