Singular Leadership in Islam

“The word imamah denotes the succession (khilafah) of prophethood in the protection of the deen and the management of the worldly affairs, and its contracting to the one who fulfils it in the ummah is an obligation by consensus...”
(Imam al-Mawardi [d. 450 AH], al-Ahkam al-Sultaniyyah, p.56)

“They (scholars of ahl al-sunnah) said regarding the khilafah and imamah that the Imamah is an obligation obligated on the ummah to the end of establishing the imam who would appoint for them judges and ministers, secure their frontiers, mobilise their armies, divide the fay’, and give justice to the oppressed from the oppressors; and they said that the way of contracting the imamah for the ummah is by their choice through exertion of effort.”
(Abd al-Qahir al-Baghdadi [d. 429 AH], al-Farq bayn al-Firaq, p.340)

“All of ahl ul-sunnah agreed, as did all the murji’a, all the shi’a, and all the khawarij upon the obligation of the Imamah, and that it is obligatory on the ummah to submit to a just imam, who establishes upon them the ahkam of Allah, and manages their affairs by the ahkam of the shari’a with which the Messenger of Allah (saw) came; except only the najadat from the khawarij who said: the people are not obliged with the imamah, rather what is upon them is to mutually practice the what is correct between them.”
(Ibn Hazm [d. 456 AH] al-Fasl fi Milal wa ‘l-Ahwaa’ wa ‘l-Nihal, 4:87)

“The Imamah is a complete authority and general leadership over all the people in all important religious and temporal affairs. Its roles includes the defense of the territory of dar al-Islam, looking after the interests of the community, establishing the Islamic da’wah by providing evidence and proof and by the sword, restraining deviation and inequity, providing help and support to the oppressed against transgressors and recovering dues from those who refuse to fulfill them and providing them to those who were deprived of them…the companions of the Messenger of Allah (saw) saw that moving swiftly to appoint the imam was the right thing to do; thus they left the preparation of the Prophet’s burial because of being engaged in this task, fearing lest a tribulation encompass them.”
(Imam al-Haramayn al-Juwayni [d. 478 AH], Ghiyath al-Umam fi Tiyath al-Dhulam, 1:22-23)

“Hence it is clear that an executive authority (sultan) is necessary for the organisation of the dunya, and the organisation of the dunya is necessary for the organisation of the deen, and the organisation of the deen is necessary for success in the hereafter and that is the objective of the prophets without doubt. Therefore the obligation of appointing an imam is from the necessities of the shari’a that simply cannot be left, so know this.” “If the Imamah becomes void so too would the delegation (of authority). The judges would dissolve and join the ranks of the people. Proper legal disposal of rights with respect of life, blood, honour and wealth would be prevented, and application of the shari’a would end in all these important matters.”
(Imam al-Ghazali [d. 505 AH], al-Iqtisad fi al-I’tiqad: 199 & Fada’ih al-Batinah: 105 respectively)

“When the death of Abu Bakr (ra) neared he said (to the sahaba), “Consult amongst yourselves about this matter (of khilafah)”. He then described the attributes of Umar (praising him) and chose him as successor. It did not occur to his heart, or that of anyone else, in the least, that it is permissible for there to be no imam. When the death of Umar (ra) neared he made the matter one of consultation between six, and they consented upon Uthman (ra), and after that upon Ali. All of this indicates that the sahabah (ra), the first and best of the Muslims, consented that having an imam was necessary…This type of consensus is a definitive evidence for the obligation of the imamah.”
(Imam al-Shahrastani [d.548 AH], Nihayat al-Iqdam fi ‘Ilm al-Kalam, 1:268)

“This ayah is an evidence for the appointment of an