The overall approach of the Caliphs toward Imam Reza (A.S)
Imam Reza (A.S) faced different situations during the tenure of the Imamate.
At beginning, the tenure of Imam Reza's Imamate was along with Aaron, who seemed to be in the peak power when Imam Kazem (A.S) was martyred by him. He tried hard to struggle against the Imam (A.S) and his followers. He imprisoned many Shi'a leaders and chased the others; ibn – iAbi Amir's story is prominent and famous.
Aaron's having died and Ma'mun fighting his brother, Amin, to seize power which preoccupied Abbasid government for a period of time made a different situation for the Imam (A.S) compared with Aaron's period since they were worried about the complete destruction of their government and it was an appropriate opportunity to develop education among Shi'a followers. The communication among Shi'a was very strong and better than before in these periods.
Ma'mun's victory changed drastically the condition. He devised a new policy in dealing with Imam Reza (A.S) and his followers. It was a task which had never been done and it might be the most dangerous task to harm Shi'a's organization.
Ma'mun invited the Imam (A.S) to Khurasan, which was called Marv, without fighting the Imam (A.S) and respecting him. He conducted a scenario and if Imam's tact didn't exist, he could have terribly influenced the configuration of Shi'a's organization. But the Imam (A.S) neutralized Ma'mun's guile as if that plan was changed to a program in which the Imam (A.S) managed to develop Shi'a and his organization as if he was killed in this way.
There were some interpretations of Ma'mun's invitation of Imam Reza (A.S) including: strengthening his power by Imam (A.S)'s presence, eradicating Alawi's movement around his government, attracting Abbasid to himself in order for them not to join Alawi and not to eradicate his power.
Imam Reza (A.S) mentioned the reason of his invitation to Khurasan by Ma'mun which was the destruction of Imam's personality in order to dominate Shi'a. Ma'mun's fathers attempted unsuccessfully to reach this purpose by coercive methods, Shi'a developed more and more and it was so deeply penetrated in Abbasid government that some of their ministers were Shi'a.
To clarify this point, we will narrate the story of Imam's summoning briefly quoted by "Aba Salt Heravi", who accompanied the Imam (A.S) in Marv and witnessed the events closely. This dialogue occurred after Imam Reza (A.S)'s summoning.