Yaḥyā ibn ʿAbd Allāh ibn al-Ḥasan ibn al-Ḥasan ibn ʿAlī ibn Abī Ṭālib (; –803) was an Alid and Zaydi leader who led a rebellion against the Abbasid caliph Harun al-Rashid in Daylam in 792. He was soon obliged to capitulate, but his activity began the spread of Zaydi Islam in the remote mountains of Daylam. After his surrender, he was initially treated with much honour, but Harun remained deeply suspicious of his popularity and intentions, and recalled him to Baghdad, where he spent the remainder of his life in prison. In 802, the Barmakid Ja'far ibn Yahya helped him escape, but he was captured; the event led to the execution of the Barmakids, once Harun's closest companions. Yahya died in prison, probably in 803.
Biography
Origin and early life
Yahya was a great-great-grandson of Ali ibn Abi Talib, the son-in-law of Muhammad and first Shi'a imam. His mother, Qurayba bint Rukayh, was one of the wives of his father, and niece of the mother of his half-brothers, Muhammad al-Nafs al-Zakiyya and Ibrahim.
Yahya was born around 745/6. Shortly after his birth, in 748–750, the Abbasid Revolution overthrew the Umayyad Caliphate (661–750) and established the Abbasid dynasty at the helm of the Islamic world. The change of dynasty was not a mere succession struggle, but the culmination of a broad social and political movement that rejected the Umayyad regime, which was widely regarded as oppressive, too dependent on and favouring its Syrian heartland to the exclusion of other areas, and more concerned with the worldly aspects of the caliphate than the teachings of Islam. A widespread belief at the time favoured replacing Umayyad dynastic rule with that of a "chosen one from the Family of Muhammad" (), who alone would have the divine guidance necessary to interpret the Quran and create a truly Islamic government that would bring justice to the Muslim community, treating all Muslims equally regardless of their origin. In the first instance this meant the Alids, who claimed descent from Muhammad via Ali ibn Abi Talib, and to whom Yahya's family belonged. However, the Abbasids exploited the vagueness of the slogan by portraying themselves as also being members of the wider "Family of the Prophet" through their common descent from the Banu Hashim clan. This claim was rejected by later Shi'a writers, who restricted membership in the Family of the Prophet to the Alids and thus considered the Abbasids as usurpers, but this distinction was not so clear-cut at the time, and the Abbasid claims appear to have been widely accepted when they came to power. As a result, the relationship between the Abbasid dynasty and the Alids was ambivalent and underwent many changes. The Abbasids tried to secure Alid support, or at least acquiescence, to their rule through the award of salaries and honours at court. Nevertheless, many Alids, chiefly of the Zaydi and Hasanid (to which Yahya belonged) branches, continued to reject the Abbasids as usurpers, and several went into hiding and once again tried to rouse the discontented against the new regime.
As a result of these tensions, Yahya's father was imprisoned by the Abbasid caliph al-Mansur () in 758, and Yahya was taken in and brought up by Ja'far al-Sadiq, a noted scholar who is considered as the sixth imam of the Imami (i.e., Twelver and Isma'ili) branches of Shi'ism. Al-Sadiq made Yahya one of his deputies, and was a major influence on Yahya's own legal opinions, and his utterances on legal matters are held in high regard by Imami scholars, as transmissions of al-Sadiq's views. In 762–763, Yahya's half-brothers, Muhammad al-Nafs al-Zakiyya and Ibrahim launched a major but unsuccessful rebellion against al-Mansur at Medina and Basra. Yahya was too young to take part in the uprising, but, along with his brother Idris, he played a prominent role in the revolt of his nephew, al-Husayn ibn Ali al-Abid, that ended at the Battle of Fakhkh, near Mecca, in 786.