First Journey to Iraq When Mamun appointed Imam Reza (AS) as...

First Journey to Iraq When Mamun appointed Imam Reza (AS) as his heir apparent the imperatives of his diplomacy demanded that leaving aside Bani Abbas he should level up his relations with Bani Fatima in order to gain the favor of the followers of the Ahle Bait.

He felt that, beside the demonstrations of his sincerity and solidarity with them, it was necessary that the old bonds that already existed between them by virtue of their belonging to the same Hashimite clan should be revived and the foundations of a new relationship should be laid.

Therefore in the same ceremonial function in which Imam Reza (AS) was made his heir apparent, Mamun also solemnized the marriage of his sister Umme Habiba with Imam Reza (AS) and announced the engagement of his daughter, Ummul Fazl, with Imam Muhammad Taqi (AS). Most probably, he was under the impression that he would thereby be able to bring Imam Reza (AS) completely to his side.

But when he realized that the Imam (AS) would not at any cost be prepared to relinquish the obligations that devolved upon him in his capacity as the successor of the Prophet (SAW) and now, being a pillar of the Abbassid State, his continued adherence to those principles was much more dangerous than when he was living a life of seclusion in the locality of Bam Hashim in Medina, with a view to safeguarding the interests of his rule, found it necessary to end the life of Imam Reza (AS) through poisoning.

In so far as the constraints behind the appointment of Imam Reza (AS) as the heir apparent were concerned i.e., to keep the Iranians and the Shiite community under his control, they were still there.

Therefore, on the one hand he exhibited extraordinary sorrow and grief on the demise of Imam Reza (AS) to show that he had nothing to do with the unjust killing of the Imam (AS) and, on the other hand, he deemed engagement of his daughter with Imam Muhammad Taqi (AS) With this end in view, he called Imam Muhammad Taqi (AS) from Medina to Iraq as after the demise of Imam Reza (AS) he himself had shifted from Khurasan to his old dynastic capital, that is, Baghdad.

He was determined to get Ummul Fazl married to Imam Muhammad Taqi (AS) without any delay. Disputation with Religious Scholars The very act of Mamun’s nomination of Imam Reza (AS) as his heir apparent was intolerable to the Bani Abbas. With the demise of Imam Reza (AS) they heaved a sigh of relief.