(iv) The fourth instance was the occasion of the invasion of Tabuk. To understand the occasion and the cause of remarks of the Holy Prophet, it is necessary to know the historical background of the incident. It was the summer of 9 A.H. and the Holy Prophet had received the information that the Roman King was mobilising his forces to invade the Islamic state. He decided to face them in their own land and not to allow them the run of the Muslim state. The situation had become very serious because there was famine in Hijaz, Tayef and Yaman. The Hypocrites were carrying on intensive propaganda that the famine was the sign of the wrath of gods, who wished to exterminate the Muslim with the worst form of death. It was therefore imperative that the state should be left in the hands of a powerful guardian as otherwise there was every possibility of being crushed between the two enemies, the Romans and the Hypocrites. The Holy Prophet therefore decided that Hazrat Ali should act as a regent in his place and the world might also realize that in the opinion of the Holy Prophet none could look after the temporal as well as the spiritual welfare of the Muslims during his absence except Hazrat Ali. The Holy Prophet called Hazrat Ali and told him that he would have to act a regent for him, saying: "O Ali nobody could look after this Centre of Muslim state but you and I." Hazrat Ali's stay at Medina disappointed the hypocrites, and as they constituted the majority of those left behind, they started a whispering campaign against Prophet Muhammad to the effect that the Prophet had lost faith in Hazrat Ali. Annoyed at this, Hazrat Ali left Medina immediately and met the Prophet at Jerf where he informed him of all that had passed. Thereupon, the Holy Prophet said: "O Ali! they are lying against you as they have lied against me. They have called me an epileptic, a magician, a sorcerer and a necromant. I have appointed you as my Vicegerent and my Caliph over all whom I left behind. Are you satisfied to realize that you are unto me as Harun was unto Musa?" Reference:(1) Musthadrik of Imam Hakim (2) Istheeaab of Allam Ibne Abdul Bur (3) Izalathul Khifa of Shah Waliullah (4) Thuzakera-e-Khavas-ul-Aaimma of Subth Ibne Jauzee (5) Sahee Bokhari Para 18, Page 89; Para 145, page 387 (v) It was the occasion of the return journey from the performance of 'The Farewell Pilgrimage' during a halt at a place called Khumm. Prophet Muhammad had summoned an assembly of the people accompanying him, and used words which could leave little doubt as to his intention regarding a successor.