Birth and early life Ali was born in Medina in , , or . The first date is said to be based on a prediction ascribed to his grandfather, al-Sadiq, who died in that year, that the successor to his son al-Kazim would be born soon. There are some indications that Ali might have been born as late . In any case, the date often given by Shia authorities is 11
Du al-Qa'da . His father was al-Kazim, the seventh Twelver Shia Imam, who was a descendant of
Ali and
Fatima, cousin and daughter of the
Islamic prophet, respectively. His mother was a freed slave, probably of
Berber origin, whose name is recorded differently in various sources, perhaps Najma or Tuktam. It was reputedly
Ja'far al-Sadiq, the father of al-Kazim, who chose Najma for him. Momen writes that Ali was thirty-five years old when his father died, whereas Donaldson holds that he was twenty or twenty-five at the time.
During Harun's rule Al-Rida lived with his father Musa al-Kazim in Medina until . When Harun arrested Musa and transferred him to Iraq, he took care of Musa's property and the affairs of the Shias as the attorney of his father. With the death of Musa al-Kazim in Baghdad prison in Rajab , his son Ali al-Rida became his heir and successor, according to his father's will. According to Madelung, al-Kazim had appointed al-Rida as his executor and al-Rida also inherited his father's property near Medina, excluding his brothers. According to Musa al-Kazim will, the custody of his children, wives and property was also entrusted to Ali al-Rida. Ali spent the next ten years of his life—from to —in the reign of Harun.
Civil war and unrest The Abbasid caliph Harun died during the
imamate of al-Rida and the empire was split between his two sons: the reigning caliph, al-Amin, who was born to an
Arab mother, and al-Mamun, who was born of a Persian mother and was designated as the successor and the governor of the province of
Khorasan in present-day Iran. In effect, according to
Momen, al-Amin controlled Iraq and the west with his Arab , al-Fadl ibn Rabi, while al-Mamun controlled Iran and the east with his Persian ,
al-Fadl ibn Sahl. Al-Amin reportedly violated these arrangements by appointing his son as successor in place of Mamun, and soon a civil war ensued in which al-Amin was killed and Baghdad was occupied by al-Mamun's general, who nevertheless remained in
Merv in Khorasan, apparently determined to make there his new capital. Al-Rida, who, according to a tradition narrated by Ibn Babawayh and al-Tabarsi, had informed one of his companions that Ma'mun would kill Amin, kept himself away from the conflicts between the two. The period of Amin's caliphate is said to be the time of peace for al-Rida, during which he found the opportunity to fulfill his mission of spreading the Islamic teachings. Al-Mamun claimed for himself the title of Imam al-Huda (), possibly to imply that he was best qualified for the caliphate. Notably, he faced costly revolts in Kufa and Arabia by
Alids and
Zaydis, who intensified their campaign against the Abbasids around 815 CE, seizing the cities of
Mecca,
Medina,
Wasit, and
Basra. In particular, the Shia revolt by
Abu'l-Saraya in 815 was difficult to suppress in Iraq, and compelled
al-Hasan ibn Sahl, al-Mamun's governor of Iraq, to deploy the troops of the Khorasani general
Harthama. Throughout the years, several of al-Rida's brothers and his uncle Moḥammad ibn Ja'far participated in the Alid revolts in Iraq and Arabia, but al-Rida refused any involvement. In this period, al-Rida's only involvement in politics might have been to mediate between the Abbasid government and his uncle Muḥammad ibn Ja'far, who had revolted in Mecca.
Appointment as heir apparent , minted at
Isfahan in 817, citing al-Ma'mun as caliph and Ali al-Ridha as heir apparent ()|alt=Photo of both sides of a silver coin with Arabic inscriptions Departing from the established anti-Shia policies of his predecessors, al-Mamun invited al-Rida to Khorasan in 816 CE, and designated him as successor in 817. According to Madelung, al-Mamun wrote to al-Rida in , invited him to come to Merv, and also sent Raja ibn Abi'l Zahhak, cousin of his , and a eunuch to accompany al-Rida on this trip. In the same year, al-Rida might have also made the pilgrimage to Mecca with his five-year-old son
Muhammad al-Jawad. After some initial resistance, al-Rida set out for Merv in 816. According to a narration that some ancient sources have confirmed, Ma'mun had ordered that the Imam not be taken via
Kufa and
Qom, as he was worried that the feelings of the Shias of these cities in their friendship with the Imam would create problems for him (Ma'mun). Though he did not pass through Qum on his way to Merv, he stayed for some time in
Nishapur, where prominent Sunni traditionists visited him, including Ibn Rahuya, Yahya ibn Yahya, Moḥammad ibn Rafe', and Ahmad ibn Ḥarb. Al-Rida continued on to Marv after receiving a new summons from al-Mamun. A number of Sunni hadith scholars also asked al-Rida to narrate a hadith for them that has become known as the
Hadith of Golden Chain. In Merv, al-Mamun first offered al-Rida the caliphate, though this was turned down by the latter. According to Madelung, al-Rida resisted al-Mamun's proposals for about two months until he reluctantly consented to an appointment as heir to the caliphate. The sources seem to agree that al-Rida was reluctant to accept this nomination, ceding only to the insistence of the caliph, with the condition that he would not interfere in governmental affairs or the appointment or dismissal of government agents. On 2 Ramadan 201 AH (23 March 817) by one account, the dignitaries and army leaders in Merv pledged their allegiance to the new heir apparent, who was dressed in green. An official announcement was made in the mosques throughout the empire, coins were minted to commemorate the occasion, and al-Mamun also changed the color of uniforms, official dress, and flags from black, the official Abbasid color, to green. This move possibly signified the reconciliation between the Abbasids and the Alids. To strengthen their relations, al-Mamun also married his daughter to al-Rida and promised another daughter to al-Rida's son in Medina, a minor at the time.
Motives The motivations of al-Mamun for this appointment are not fully understood. At the time, he justified his decision by maintaining that al-Rida was the most suitable person for the caliphate. The reluctance of al-Rida in accepting this designation, however, might reflect his suspicion that al-Mamun had ulterior motives. With an age gap of more than twenty years, it also seems unlikely that al-Rida would ever have succeeded the much younger al-Mamun. With this appointment, some have suggested that al-Mamun hoped for the support of the Shia and respite from their numerous revolts. Others have suggested that al-Mamun was influenced by his powerful Persian , af-Fadl ibn Sahl, who had Shia tendencies. Madelung, however, finds it more likely that the initiative to appoint al-Rida belonged to al-Mamun and not his . Some authors have not found the appointment surprising, noting the strained or severed relations of the caliph with his Abbasid relatives. Yet others have written that al-Mamun wanted a merit-based caliphate, though he made no mention of rules governing the succession to al-Rida during the ceremony. It has been suggested that al-Mamun might have wanted to heal the Sunni-Shia division, while
Lapidus and others hold that al-Mamun wanted to expand his authority by adopting the Shia views about the divine authority of religious leaders, alongside his later religious inquisition (). Bayhom-Daou considers it likely that al-Mamun saw this appointment as a means of discrediting the Shia doctrine of Imamate, and Tabatabai writes that al-Mamun might have also hoped to undermine the position of al-Rida as a Shia religious leader by engaging him in politics. Al-Rida's rejection of al-Mamun's initial offer for replacing him as the caliph has been used to argue that al-Rida's ultimate aim was not temporal and political power. Rather, Mavani suggests that such power was merely a means for the Imam to reach the ultimate goal of guiding the community to salvation. When al-Rida was asked why he accepted the successorship, he is reported to have emphasized his unwillingness, responding, "The same thing which forced my grandfather the Commander of the Faithful [Ali ibn Abi Talib] to join the arbitration council [i.e.,
coercion]". To show his dissatisfaction with the trip to Khorasan, as reported by Ibn Babuyyah, al-Rida not only refused to take his family with him but also asked them to cry loudly for him, saying that he would never return to his family's embrace. It also appears that this appointment did not alienate any of the followers of al-Rida which, according to Bayhom-Daou, might imply that they were convinced that he was a reluctant player who had no choice but to accept his designation as the heir apparent.
Reactions Perhaps incorrectly, the appointment of al-Rida was at the time largely attributed to the influence of al-Mamun's Persian , al-Fadl ibn Sahl. Nevertheless, various Abbasid governors, with the exception of Ismail ibn Jafar in Basra, loyally carried out their orders and exacted the oath of allegiance to the new heir. The appointment of the Alid al-Rida by the Abbasid al-Mamun apparently brought him the support of several notable Alids and nearly all the Zaydite partisans. It also immediately invoked strong opposition, particularly among the Abbasids and Arab Sunni nationalists. Al-Mamun's decision did not carry the public opinion of the Iraqis, who declared him deposed and installed Ibrahim ibn al-Mahdi, another Abbasid, as caliph in 817, while the popular militia roamed through Baghdad, demanding a return to the Quran and the
Sunna. Ibrahim, a half-brother of al-Mamun's father, is said to have been a weak statesman and a mere figurehead, whose rule was largely confined to Baghdad. There were also military engagements in Baghdad, Kufa, and Wasit between al-Mamun's forces and the supporters of Ibrahim who were themselves much harassed by financial and logistical difficulties.
Tenure as heir apparent Al-Rida was given a high status at the court of al-Mamun. While the caliph evidently desired that al-Rida should immediately engage in all official ceremonies, the latter is reported to have refrained, stipulating that he would not participate in government affairs. Al-Rida was given his own police force and guard, as well as a chamberlain and a secretary. The caliph is said to have relied on the judgment of al-Rida in religious questions and arranged for debates between him and scholars of Islam and other faiths. According to Rizvi, however, these religious disputations seem to have been designed as set pieces to embarrass al-Rida. Their accounts were later recorded by
Ibn Babawayh in his
Uyun akhbar al-Rida. Return to Baghdad The seriousness of the civil unrest in Iraq was apparently kept hidden from al-Mamun by his until 818, and it was al-Rida who urged the caliph to return to Baghdad and restore peace. Al-Rida's assessment was supported by several army chiefs and al-Mamun thus left Khorasan in 818. Before their return, his offered his resignation, pointing out the hatred of the Abbasids in Baghdad for him personally, and requested the caliph to leave him as governor in Khorasan. Al-Mamun instead assured the of his unrestricted support and published a letter to this effect throughout the empire. However, six months later, in
Sha'ban 202 (February 818), the was assassinated in
Sarakhs by several army officers as he accompanied al-Mamun back to Baghdad. Those responsible were soon executed, but not before declaring that they had been acting on the orders of the caliph. Henceforth, al-Mamun governed with the help of counsellors on whom he did not confer the title of . == Death and burial ==