البجا
The Rabi'ah emerged as the strongest of the Arab tribes inhabiting the Egyptian-Nubian frontier region. By the 10th century, they were running a principality that replaced that of al-Umari's. The Rabi'ah was able to grow powerful because of their alliance with the indigenous Beja people, namely the Muslim Hadariba tribe, which controlled the region between the Red Sea coastline and the eastern banks of the Nile River. The alliance manifested in business partnerships in the mining industry and intermarriage, including between the chiefs of the two tribes. The sons of Rabi'ah father and Hadariba mothers inherited the lands and titles of their maternal grandparents since Beja inheritance prioritized descent from the mother. Thus, by 943, Ishaq ibn Bishr, who was born to a Rabi'ah father, became the chief of the Rabi'ah-Hadariba principality after succeeding his maternal Beja uncles Abdak and Kawk. According to the 14th-century Arab historian Ibn Fadlallah al-Umari, the Rab'iah and Beja "became like one" during Ishaq's reign. The latter was killed during an intra-tribal war in Wadi Allaqi, and was succeeded by a paternal cousin from Bilbays, Abu Yazid ibn Ishaq. Abu Yazid established Aswan as the principality's capital and was recognized by the Fatimid Caliphate, which controlled Upper Egypt, as the "protector of Aswan".