i.e. "kill all your brothers."
"The more generally accepted view of the Sunni Muslims was that the caliphate was elective, and any member of the Quraysh, was eligible... But the patriarchal caliphate ended in regicide and civil war, and with it the experiment in elective sovereignty. Thereafter, the caliphate became, in practice, even if not in theory, hereditary in two successive dynasties, the Umayyads and the Abbasids. The elective principle remained strong enough to prevent the emergence and acceptance of any regular rule of succession, such as the primogeniture of the European monarchies." -- The Middle East, Bernard Lewis.
Basically, Islamic succession was originally elective. When that system failed, it became hereditary, but with a twinge of "electiveness" in the sense of a military election, i.e. civil war. Each pretender would be backed by his electorate (various supporting generals and the soldiers) and they would contest succession in the court of the battlefield.
"The more generally accepted view of the Sunni Muslims was that the caliphate was elective, and any member of the Quraysh, was eligible... But the patriarchal caliphate ended in regicide and civil war, and with it the experiment in elective sovereignty. Thereafter, the caliphate became, in practice, even if not in theory, hereditary in two successive dynasties, the Umayyads and the Abbasids. The elective principle remained strong enough to prevent the emergence and acceptance of any regular rule of succession, such as the primogeniture of the European monarchies." -- The Middle East, Bernard Lewis.
Basically, Islamic succession was originally elective. When that system failed, it became hereditary, but with a twinge of "electiveness" in the sense of a military election, i.e. civil war. Each pretender would be backed by his electorate (various supporting generals and the soldiers) and they would contest succession in the court of the battlefield.