The series "The Caliphate and Imamate in Islamic Thought" - By the writer and thinker Thaer Salama - Abu Malik - Part 41
Their consensus has been reached on the obligation to establish the caliphate, and no one deviated from that. This transmission about the occurrence of this consensus on this matter has been transmitted to us through a recurrent transmission, so it is definitive. We will give a few examples of what some scholars have decided: A- Ibn Khaldun said (in the Introduction): "Indeed, the appointment of the Imam is obligatory, and its obligation has been known in Sharia by the consensus of the Companions and the Followers; Because the companions of the Messenger of God, may God bless him and grant him peace, upon his death, rushed to pledge allegiance to Abu Bakr, may God be pleased with him, and hand over consideration of their affairs to him, and so in every era after that, and people were not left in chaos in any era, and that became a consensus indicating the obligation to appoint the Imam." That is, the nation transmitted this consensus and it was established among them generation after generation, and class after class, so the existence of the consensus is recurrent.