Musnad Ahmad 825:2

Abu Sa’id, the freed slave of Banu Hashim, and Hashim ibn al-Qasim narrated to us, they said: Muhammad ibn Rashid narrated to us, Makhul narrated to us, from ‘Abdullah ibn Hawalah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "There will be an army in al-Sham, and an army in Yemen." A man said: "Choose for me, O Messenger of Allah, if that happens." The Messenger of Allah (peace and blessings of Allah be upon him) said: "You must go to al-Sham, you must go to al-Sham" — three times — "you must go to al-Sham. Whoever refuses, let him join his Yemen, and let him drink from its ponds, for Allah has guaranteed for me al-Sham and its people." Abu al-Nadr said twice: "Let him join his Yemen."