Musannaf Ibn Abi Shayba 37:396

Hussain bin Ali narrated to us, from Za'idah, from Abd al-Malik bin Umayr, from Jabir bin Samurah, from Nafi' bin Utbah bin Abi Waqqas, from the Prophet (peace be upon him), who 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." Jabir said: "The Dajjal will not emerge until the Romans are opened."