Musnad Ahmad 484:1

Abu al-Yaman narrated to us, Abu Bakr—meaning Ibn Abi Maryam—narrated to us, from Abd al-Rahman ibn Jubayr ibn Nufayr, from his father, who said: The companions of Muhammad, may Allah bless him and grant him peace, narrated to us that the Messenger of Allah, may Allah bless him and grant him peace, said: "Ash-Sham will be opened for you. So when you are given the choice of dwellings therein, you must take a city called Damascus, for it is the stronghold of the Muslims during the great battles (al-malahim), and its military camp (fustat) is in a land called al-Ghuta."