What is the greatest obligation in Islam?

What is the greatest obligation in Islam? Simply put - Khilafah. The famous muhaddith Abdullah ibn Mubarak (ra) (d. 181 AH) noted: "Indeed the jama'ah (body politic) is the rope of Allah, so hold on. How many a darkness does Allah repel by the sultan If not for the Khalifah, paths would not be safe for us to its grip, firm for him who professes Islam in our deen mercy results from him and in our dunya and the weak would be a source of pillage for the strong..." (Hilyat al-Awliya, 8:164) Jalal al-Din al-Suyuti noted: "The people must appoint an Imam who serves their interests like guarding the borders, preparing the armies and defeating the enemy and spies, because of the consensus of the Companions after the death of the Prophet (saw) to appoint an Imam, they even made it the most important obligation, and gave it priority over his burial, and people in every era followed it." (Sharh al-Mahali ala Jamm al-Jawami, 2:487) Ibn Taymiyyah (d. 728 AH) said: "It is imperative to know that the office in charge of governing the people is one of the greatest obligations of the deen. Nay, there is no establishment of the deen or the dunya except by it... For this reason, it has been narrated that, "The sultan is the shade of Allah on Earth", and it is said, "Sixty years of an oppressive imam is better than one night without any leader," and experience substantiates this. Thus did the salaf such as al-Fadl ibn Iyad and Ahmad ibn Hanbal used to say, "If we had one du'a guaranteed to be answered, we would supplicate for the sultan." (al-Siyasah al-Shar'iyyah, p.129) Al-Taftazani (d. 791 AH) explained: "The adoption is that it is obligatory upon the servants by textual evidence because of the saying of the Messenger, "Whoever dies not having known the Imam of his time, dies the death of the days of ignorance." Also, the Ummah agreed that this was the most important duty following the death of the Messenger, so important in fact that they considered it more important than the matter of his burial, and so also has it been after the death of each Imam." (Sharh al- Aqa'id al-Nasafiyyah, pp. 353-354) Zakariyah Al-Ansari (d. 926 AH) said: People must appoint an Imam who serves their interests, like guarding the borders, preparing the armies and defeating the enemy and spies. This is because of the consensus of the Companions after the death of the Prophet (saw) to appoint an Imam; they even made it the most important obligation and gave it priority over the burial of the Prophet (saw), and people in every era adopted this. (Ghayat al-Wusul fi Sharh Lub al-Usul, p. 420) Al-Mawardi (362-448 AH) argued: "Imamah is prescribed to succeed Prophethood as a means of protecting the Deen and of managing the affairs of this world. There is a consensus of opinion (amongst the scholars) that the person who discharges the responsibilities of this position must take on the contract of Imamah of the Ummah." (al-Ahkam al-Sultaniyyah, p. 56) Imam al-Haskafi (d. 1088 AH) said: "The major imamah (khilafah) is the right of general disposal over the people. Its study is in scholastic theology and establishing it is the most important of obligations. For this reason did the sahabah gave it priority over the burial of the Prophet (saw)..." (Radd al-Muhtar ala al-Durr al-Mukhtar, 1: 548)​​​​​ Ghazali (d. 505 AH) stated: "You should know the obligation of appointing an Imam is from the necessities of the Shari'ah which we cannot abandon... Well-ordered religious affairs are achieved through knowledge and worship. These cannot be achieved without the health of the body, the maintenance of life, the fulfillment of needs – such as those for clothing, shelter and food – and security from the onset of calamities..." (al-Iqtisad fi al-I'tiqad, p. 19) Al-Shatibi (d. 790 AH) the well known Maliki jurist observed: "In the absence of the Khilafah, a state of anarchy and lawlessness would prevail and this would usher in a great corruption and disorder. And it is evident the establishment of the Deen is impossible in a state of anarchy and disorder." (Al-Itsam) Iraqi scholar Sheikh al-Zahawi (1314 AH) said: "The Companions of the Prophet have unanimously agreed upon appointing him to office (ijma'a ala nasabihi) after the passing away of the Prophet to the extent that they considered it to be the most important of obligations (ahamm al-wajibat) giving it precedence even over his burial and people in every generation since have not stopped doing this. Also, many narrations support this [obligation of appointing an Imam] one of them being his saying "Whoever dies and does not have on his neck a pledge of allegiance (bay'ah), he dies a death like in the days of ignorance."' (Al-Fajr as-Sadiq fi-r-Radd ala Munkiri-t-Tawassul wa-l-Khawariq) Dr. Diaa al-Din Al-Rayes said: "Khilafah is the most important religious position and it is important to all Muslims, and the Islamic law stipulated that the establishment of the Khilafah is a main obligation of the duties of the Deen, but is the greatest obligation because the implementation of all other obligations depends on it." (p. 99) "The scholars of Islam have unanimously agreed-as mentioned before- that the Khilafah or Imamah is one of the fundamental obligations of the Deen, rather, it is the first or most important obligation because the implementation of other duties and the realization of the general interests of Muslims depend on it. Therefore, they called this position "the great Imamah" contrary to the Imamah of prayer which is called the "Minor Imamah". This is the view of Ahl Al-Sunnah Wa Al-Jama'a; they are the great majority of Muslims and it is the opinion of the senior Mujtahids; the four Imams and scholars such as Al-Mawardi, Al-Juwayni, Al-Ghazali, Al-Razi, Al-Taftazani, Ibn Khaldoon and others who are the imams who Muslims follow in rules of the Deen, and we have known the evidence and proofs which they used on the obligation of the Khilafah." (p. 341) The Late Shaykh 'Abd al-Qadir al-Murabit stated: "Khalifate is not only fundamental to Islam, it is the necessary foundation of its power." (The Return of the Khalifate) The Algerian Sheikh Ali Belhadj said: "The restoration of the Khilafah is of the greatest duties of the Deen: "Khilafah on the method of Prophethood". How can it not be. It is the greatest duty since the scholars of Islam and its famous people decided that the Khilafah is the basic obligation from the duties of this great Deen, but is "the greatest obligation", upon which the establishment of other duties depend. Neglecting the establishment of their obligation is one of the "greatest sins", and the loss, confusion, disputes, and the conflicts between Muslims, as individuals, and between the Islamic people, as countries, are only because the Muslims neglected the establishment of this great duty." (I'adat al-Khilafah) Sheikh al-Taher Ibn Ashour said: "Muslims did not differ after that in the obligation of establishing a Khaleefah except the odd insignificant some of the Khawarij and Mu'tazila who violated the agreement, so they were not given attention. And due to the status of the Khilafah in the foundations (Usul) of Shari'ah, the scholars linked it to the foundations (Usul) of the Deen and its issues. One of its sections was on the Imamate (Imamah). The Imam of the Two Holy Mosques [Abu Al-Ma'ali Al-Juwaini] said in Al-Irshad: "Discussion on the Imamate is not from the foundation of belief; but it is more dangerous to commit a mistake in it than being ignorant of one of the foundations of the Deen" (Usul Al-Nitham al-Ijtima'i fil-Islam, pp. 206-207)