Bayʿa, primarily a contract pertaining to the purchase of merchandise, but acquiring the meaning of a contractual obligation or covenant in general, and of political allegiance in particular. In the context of mysticism, it denotes the spiritual oath of allegiance given by a disciple to a spiritual master.

The bayʿa became the dominant method in Islamic civilisation whereby individuals pledged an oath of allegiance to their rulers. Most oaths of fealty in the time of the Prophet and the caliphs were sealed by shaking hands with the ruler, but …