Wali al-Ahd

[1] The title itself is ambiguous, as the term walī can mean both 'possessor of' or 'successor to', and the exact scope of ʿahd, 'covenant, testament', is left unclear: it can be interpreted as the covenant of God with humanity as a whole, of the previous caliph, or of the Muslim community.

[4] In Sunni jurisprudence, the choice of successor and the act of designation is the absolute prerogative of the caliph or ruler; the oath of allegiance offered to the new heir confirmed his status, but was not a prerequisite for his legitimacy.

[4] In the Abbasid period, this became a formalized and increasingly elaborate affair, deserving of a special ceremony, in which the new heir-designate also received the pledge of allegiance from the assembled court.

[4] Uniquely, in 1013 the Fatimid caliph al-Hakim, who also combined in his person the position of imam of the Isma'ili branch of Islam, separated his succession in two: his cousin Abd al-Rahim ibn Ilyas was designated walī ʿahd al-muslimīn and heir to the caliphate, while another cousin, Abu Hashim al-Abbas ibn Shu'ayb, was designated heir to the Isma'ili imamate, with the title of walī ʿahd al-muʾminīn, 'successor to the covenant of the faithful', thereby separating the government of the Fatimid state from the hitherto state religion of Isma'ilism.

[6] In modern times, the term has been revived for the crown princes of several states, such as the Qajar and Pahlavi Iran, Saudi Arabia, Jordan, Qatar and Bahrein.