Musnad Ahmad 444:0

Narrated by Abdullah ibn Hawalah: The Messenger of Allah (peace and blessings of Allah be upon him) said: "It will come to pass that you will be divided into armies: an army in Ash-Sham, an army in Yemen, and an army in Iraq." Abdullah said: "Choose for me, O Messenger of Allah, if I reach that time." He (peace and blessings of Allah be upon him) said: "You must go to Ash-Sham, for it is the chosen land of Allah among His lands, to which He gathers the best of His servants. But if you refuse, then go to your Yemen and drink from its cisterns, for Allah has guaranteed for me Ash-Sham and its people."