Musnad Ahmad 716:1

Yazid narrated to us, Mas'udi informed us, from 'Abd al-Malik ibn 'Umayr, from Jabir ibn Samurah, from Nafi' ibn 'Utbah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "You will fight the Arabian Peninsula, and Allah will open it. Then you will fight Persia, and Allah will open it. Then you will fight the Romans, and Allah will open it. Then you will fight the Dajjal, and Allah will open him."