His elder son Amin who had an Arab mother had the support of...

His elder son Amin who had an Arab mother had the support of the Arabs and most of the Abbasid elders, while the younger son Ma’mun had a Persian mother and was supported by the Persians. To console both factions Harun took a pledge from both his sons that after his death Amin will rule the Arab part of the Empire while Ma’mun will rule the Persian side. After Harun, his son, Amin became the caliph. At that period, the government was weakened because of Harun’s death.

Amin was drowned in corruption, so he and his governors paid no attention to Imam and his followers. Therefore, this period was peaceful for Imam and his followers. In 193 A.H., a conflict took place between his two sons Amin and Ma’mun which later led to bloody wars and finally the assassination of Amin in 198 A.H. Finally, Ma’mun became the caliph. He suppressed the rebellions and gained control of all the Islamic territory.

He gave the leadership of Iraq to one of his agents and himself settled in Merv. He then chose Faḍl ibn al-Sahl, who was an experienced politician, as his minister and counsellor. But the Alawid people were a threat to his government. After suffering torture, murder and plunder for a century, they had found the opportunity for division in government: any chance they got, secretly or openly, they opposed Ma’mun and wished to overthrow the Abbasid government.

In addition, they were successful in attracting general public opinion and gaining Muslims’ support. That was why whenever the Alawid people rose in revolt against the Abbasid dynasty, lots of people from any social class answered their call because people, especially Shias, had suffered great losses and painful tortures from the Abbasid Caliphate.

Ma’mun realized that the majority of Persians favoured the teachings of and if somehow, he could persuade the Imam of the in Medina to be by his side, he could confirm his rule there. Thus, Ma’mun sent some of his special agents to Imam Riḍa (PBUH) in Medina to force him to leave his home in Medina and go to the Abbasid ruler in faraway Tus. Thus, the Imam, as if by some miracle knew what was to come, he left his wife and only son Muhammad Ibn ‘Ali al-Jawad in Medina.

Imam Riḍa (PBUH) also invited many elders of Medina mostly from Banu Hashim and told them of his call to go to the outpost of the Empire to see Ma’mun. The date of his departure was in the month of Rajab 200 Hijrah.