The tribe known originally as Al Asd (e.g. in South Arabian inscriptions), and later in the Islamic tradition as Al Azd, were considered by Arabic geographers to have originated in Yemen during the pre-Islamic era. A migration of the Al Azd out of Yemen took place in two waves, one to the west (Azd Sarat and Azd Shanua) and subsequently, from Sarat and the Hijaz, one to the east (Azd Oman).
The details of this movement are obscure but there is no doubt that by the late Sasanian period the Azd Oman were considered one of the primary tribal groups in the UAE and Oman. Indeed, speaking of the period around the time of the Islamic conquest, the historian Al Baladhuri says that the inhabitants of Oman were the Azd. It was in this milieu that the Julanda emerged as an important ruling dynasty just prior to the coming of the Prophet (PBUH).