Imam Reza was the living example of the piety of Holy prophet and the chivarly and generosity of Imam Ali ibn Abi talib .
Imam Musa was well aware of the aggressive designs of the government in power against the imate ans therefore during his life time he declared Imam Reza as his successor in the presence of hundred and seventyone prominet religious divines and called upon his sons and his family to submit to him and refer to him after his death .
Imam Reza inherited the great qualities of the head and heart from his ancestors.He was versatile person and had full command over many languages.Ibnu l Athir al-jazari penned very rightly that Imam Reza was undoubtedly the greatest scholar of the second century (A.H)
Imam Reza was the eight Imam and al Mamoon could not help holding him in great esteem because of the imam's piety,wisdom,knowledge , modesty , decorum and personality .Therefore he decided to nominate him as the rightful heir to the throne.
Even after the declaration of succession when there was every oppertunity for imam to live a splendid wordly royal life , he didnot pay any heed to material comforts and devoted himself compleatly to imparting the true Islamic conception of the Holy prophet's teaching and Holy Quran.He spent most of his time in praying to Allah and serving people.
Taking full advantage of the concessions given to him by the virtue of his elevated position in the royal court , he organized the Majalis(meetings) commemorating the martyrdom of the martyrs of Karbala.
Al-Mamoon scared of the growing popularity of the imam and he had appointed him as his heir to the throne only for the fulfilment of hisambitious and sinster designs and getting the imam's endorsement to his tricky planns.But Imam refuses to give his endorsement to any such plans which were againist islam. Al-Mamoon therefore became very disappointed wit him and decided once and for all to check his growning popularity and ensuring his own survival by actiong according to the old traditions of killing Imam.Wanting to do it he invited Imam and fed him the poisoned grapes,The imam died on the 17th Safar 203 A.H.
He was buried in meshad and his great shirne speaks well for the great personality the Imam Possessed.