Musnad Ahmad 8:101

Husayn narrated to us, from Za'idah, from 'Abd al-Malik ibn 'Umayr, and 'Abd al-Samad narrated to us, Za'idah narrated to us, 'Abd al-Malik ibn 'Umayr narrated to us, from Jabir ibn Samurah, from Nafi' ibn 'Utbah ibn Abi Waqqas, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "You will fight the Arabian Peninsula, and Allah will open it for you. Then you will fight Persia, and Allah will open it for you. Then you will fight the Romans, and Allah will open it for you. Then you will fight the Dajjal, and Allah will open it for you." He said: Jabir said, "The Dajjal will not emerge until the Romans are conquered."