HAZRAT MAHDI’S (AS) FOLLOWERS WILL NOT BE ARAB. They will be from other nationalities. BUT THEY WILL SPEAK ARABIC. (Al-Barzanji, Al-Isha'ah li-ashrat al-sa'ah)
The hadith relates that Hazrat Mahdi’s (as) followers will not be Arab and that they will be from other nationalities. However it is evident that they will speak Arabic.