Abu al-Qasim al-Husayn ibn Ruh Nawbakhti (Arabic: أَبُو ٱلْقَاسِم ٱلْحُسَيْن ٱبْن رُوح ٱلنَّوْبَخْتِيّ, ) was the third of the Four Deputies, who are believed by the Twelvers to have successively represented their Hidden Imam, Muhammad al-Mahdi, during his Minor Occultation (874–941 CE). Ibn Ruh in this role succeeded Abu Ja'far Muhammad ibn Uthman in 917 CE. After some twenty years in office, Ibn Run died in 937 CE and was succeeded by Abul Hasan Ali ibn Muhammad al-Samarri, the fourth and final deputy.
Until their deaths, the tenth and eleventh Shia Imams (Ali al-Hadi and Hasan al-Askari, respectively) were held in the garrison town of Samarra under close surveillance (or house arrest) by the Abbasids, who are often responsible in Shia sources for poisoning the two Imams. The two Imams witnessed the deterioration of the Abbasid caliphate, as the imperial authority rapidly transitioned into the hands of the Turks, particularly after al-Mutawakkil.
Contemporary to the tenth Imam, the Abbasid al-Mutawakkil violently prosecuted the Shia, partly due to a renewed Zaydi opposition. The restrictive policies of al-Mutawakkil towards the tenth Imam were later adopted by his son, al-Mu'tamid, who is reported to have kept the eleventh Imam under house arrest without any visitors. Instead, al-Askari is known to have primarily communicated with his followers through a network of representatives. Among them was Uthman ibn Sa'id, who is said to have disguised himself as a seller of cooking fat to avoid the Abbasid agents, hence his nickname al-Samman. Tabatabai suggests that these restrictions were placed on al-Askari because the caliphate had come to know about traditions among the Shia elite, predicting that the eleventh Imam would father the eschatological Mahdi.
Immediately after the death of al-Askari in 260 (874), Uthman ibn Sa'id claimed that the eleventh Imam had a young son, named Muhammad, who had entered a state of occultation due to the Abbasid threat to his life. As the special agent of al-Askari, Uthman also claimed that he had been appointed to represent the son of the eleventh Imam. Twelver sources detail that Muhammad al-Mahdi made his only public appearance to lead the funeral prayer for his father instead of his uncle, Ja'far.
Thus began a period of about seventy years, later termed the Minor Occultation (260-329 AH, 874–940 CE), during which it is believed that four successive agents acted as intermediaries between the Hidden Imam and his followers. These four agents are collectively known as the Four Deputies . An agent was also variously called deputy, emissary, and gate .
Uthman was later succeeded by his son, Abu Ja'far Muhammad, who served until his death in 304 or 305 (917 or 918 CE).
The birth date of Ibn Ruh is unknown. It is known that he was a native of Qom, located in present-day Iran, who later migrated to Baghdad during the time of the first agent, Uthman ibn Sa'id. Ibn Ruh was also a member of the al-Nawbakhti, an influential family in the Abbasid court. In view of his close ties with Abu Sahl al-Nawbakhti, the leader of the al-Nawbakhti family, Ibn Ruh is said to have been highly respected in the Abbasid court. He was also a close associate of the second agent, Abu Ja'far. It appears that Ibn Ruh was admired among the Twelvers for his scrupulous adherence to religious dissimulation ().
The second agent, Abu Ja'far, is said to have designated Ibn Ruh as his successor in the presence of some notable Twelvers in 917 CE. There, Abu Ja'far also added that this appointment was commanded by the Hidden Imam. Tusi in his writes that the appointment of Ibn Ruh was immediately confirmed with a note from the Hidden Imam, which, according to Sachedina, may suggest that some were dissatisfied with his appointment. With this note, the communications with the Hidden Imam resumed after a lapse of about twenty-five years.
Ibn Ruh's term overlapped with the caliphates of al-Muqtader, al-Qahir, al-Radi . He was often in favor with their s. However, following the 306 (918) downfall of the Banu al-Furat, the influential Twelver family in the Abbasid court, Ibn Ruh was temporarily forced into hiding and later imprisoned in 312 (924-25) by al-Muqtadir for financial reasons. It was likely around this time that an associate of Ibn Ruh, named Abu Ja'far Muhammad ibn Ali al-Shalmaghani, turned against him and claimed to be the rightful agent of the Hidden Imam, before denouncing the concept of occultation as a lie. He was soon denounced by the Twelvers and Ibn Ruh's authority was further strengthened after receiving another note attributed to the Hidden Imam. Another controversial figure was a disciple of al-Askari, named al-Karkhi, who was later condemned in a rescript, said to be written by al-Mahdi. Ibn Ruh died in 326 (937), and was buried in Baghdad. He was succeeded by Abu al-Hasan Ali ibn Muhammad al-Samarri as the fourth and last agent.