Imam, Ali son of Musa al-Reza(A.S.) was born in the reign of Abu-Ja'far Mansoor, and survived the regimes of Abbasid caliphs Mahdi, Hadi, Rasheed, Amin, and Ma'moon. During it, the major Islamic schools of thought were set up.

The religious scholars and learned men found refuge in Imam Reza(A.S.)
who argued with commentators, discussed with philosophy students and masters, refuted the claims and suspicions cast by the atheists and exaggerators, issued guidelines to the legal jurists, and stated the basis of shari'a and principles of monotheism. The legal jurisprudents, wisemen, sufis, preachers, infidels and ghulat attested to his abunant knowledge, the strength of his arguments, and his supremany in all the debates that were held between him and the foes of Islam. Muhammad, son of las Yaqtini, admits that:
"When people differed about Abul-Hassan al-Reza(A.S.),all the answers he had given to questions posed to him were collected. They totalled fifteen thousand."
The Imam's knowledges and sciences were the inheritance of the prophethood and Allah's gift to him and, in which, knowledges were discovered and facts were explained for him.
The author of 'I'lam Wara bin a'lam Huda' (Acquainting People with the Leaders of Guidance) quoted Aba Salt Harawi as saying: "I have never seen a man more knowledgeable than Ali, son of Musa al-Reza(A.S.),nor has any scholar see him without giving a testimony like mine. In his assembly, Ma'moon gathered before him a number of religious scholars, jurists of shari'a, and preachers. In the argument that took place, he defeated them all.
There remained no one who did not admit al-Reza's outstanding virtues, and his own helplessness. I heard him say: 'I used to sit with them at Rawdah. The religious scholars of Madinah were numerous, but, when one of them failed to find a solution to any question, all of them would refer to me. They would send me the questions and I would answer them.'
Abul-Salt then says: 'Muhammad, son of Ishaq, son of Musa, son of Ja'far (A.S.), used to say to his sons: 'This is your brother Ali, son of Musa, the prominent scholar of the Prophet's descendants. Ask him about anything related to the faith, and learn well what he says to you."

Social Conditions under Abbasid Rule
Life inside the Abbasid palaces has been perfectly described by historians, biographers and poets. It was a grave tribulation for the Muslim ummah.
Money was wasted on the purchase of slaves, building palaces, buying jewellery and rewarding the praising poets. Supporters were bought, and festivals and parties along with their supporters and sympathizers. Those few who were spared lived in permanent danger of death or imprisonment, with their property confiscated.
Now, let us look at some history books and see how the historians describe those times.
Historians wrote a lot about Rasheed's extravagance, his squandering of the umma's wealth, and his engagement in entertainment and frolic. We quote some narratives here:
In his book 'Tarikh Khulafa'' (History of the Caliphs) Suyooti says: "Rasheed once gave Sufyan, son of Uyayna, 100,000, rewarded Ishaq Moosili with 200,000, and rewarded Marwan, son of Abu Hafsa - With 5,000 dinars for a poem the latter recited in praise of him."
Sayooti adds that, "He was engaged in pleasure-chasing and singing."
Sayooti also says: "When Rasheed took over the 'caliphate' after the demise of his father, he took a fancy to one of his father's female slaves, He tried to seduce her. She rejected him saying, 'I am unfit for you, your father slept with me.' But, Rasheed's desire for her increaced. He sent for Abu-Yusuf ( the, then, chief of judges) and asked him: 'Is there anything you can do about this?' 'O Caliph of the Faithful! Everytime a slave claims something do you believe her? Do not believe her. She is not trustworthy!"
Ibn Mubarak, commenting on this episode, said: "I do not know what is more surprising to me: This, that who has shed Muslim blood and plundered their wealth and property, should refrain from violating the advances of the Commander of the Faithful, or this, that, the legal jurisprudent and chief justice on the earth should say (to Rasheed): 'Violate the sanctity of your father, attain your desire, and I will take all responsibility for this act!'
He adds: "After his death, Rasheed left behind one hundred million dinars and furniture, jewelery and animals to the value of one hunered nillion and twenty-five thousand dinars."

Political Conditions in which the Imam Reza(A.S.) lived
Imam al-Reza(A.S.) lived in the same critical period as his father and when his father was martyred, he became the Imam. But, the caliph, Rasheed, did not confront him, instead, he (Rasheed) said to Khalid, son of Yahya Barmaki who warned him against Imam Reza(A.S.): "What we have done to his father is quite enough for us."
But, nevertheless, Imam al-Reza(A.S.) could not stay out of the reach of the Abbasids. He was in the heart of the struggle that was going on between the Abbasids and the descendants of Imam Ali (A.S.).
The deterioration of the political conditions of the rulers had a very bad harmful effect on the people, both common, and their leaders, notabales and scholars. As a result, there emerged a voice, strong and loud, in favour of Ahlul-Bait (A.S.). It was the chiefs of Ahlul-Bait, like Imam al-Sadiq(A.S.), Imam al-Kadhim(A.S.) and al-Reza(A.S.), who were the hub around which people rallied, finding in them the hope of the umma.
Synpathy for Ahlul-Bait (A.S.) mounted and reached its climax during the leadership of Reza(A.S.). Even some senior officials and military officers expressed their sympathy with Ahlul-Bait (A.S.). While the Abbasid state was being thrown into great confusion and internal struggle between Amin and his brother Ma'moon, Imam al-Reza(A.S.) won more followers and admirers as being the leading personality from Ahlul-Bait (A.S.). Eyes were glued to him and hearts hovered around him.

Revolts and Uprisings
After Ma'moon overcame his brother Amin and took power from him, he faced continuous revolutions led by the Alawites, due to the Abbasid policy and conditions of pursuit and oppression which caused them to carry out armed movements and revolutions in order to defend the truth by force.
Ma'moon held the same view, about the Imams of Ahlul-Bait (A.S.), that his forefathers held. He led a bitter struggle with his brother Amin, while he was besieged by a number of Alawite revolts and uprisings.
Unlike his forefathers, Amin did not resort to violence against Imam al-Reza(A.S.). He ended up favouring one political choice; to make a truce with the descendants of Ali, son of Abu-Talib (A.S.), acknowledging their right to rule. He did so in order to convince people of his moderation, win over followers and relieve the umma of the atrocities of the previous Abbasid rulers. It, was, also, a good way of combatting the rising Alawite oppisition which was strengthened, greatly, by the internal disputes within the Abbasid ranks; the terrorism, bloodshed, squandering of the umma's riches, misrule, and the lapse into insecurity. Ma'moon, thus, invented a political plan to contain Imam al-Reza(A.S.). He appointed him his heir apparent, as he was the sole Imam from the Prophet (peace be upon him), and the leading, unparalleled leader of his time.

Post of Heir Apparent
The best, and probably the only possible way out of the political crisis besetting Ma'moom lay in persuading Imam Reza(A.S.) to acept the idea of being his successor. By so doing, Ma'moon thought he could win over the opposition to his side and put both the Abbasid and Alawites under his control.
Imam al-Reza(A.S.) realized the dimensions of this political scheme of Ma'moon and that, thus, he (A.S.), many times, refused what Ma'moon exposed for him. But, later on, he accepted the post after being threatened, by Ma'moon, to be killed.
Imam al-Reza(A.S.) agreed, under coercion, to accept the post, and so that he would not share the rulers' guilt over their misuse of power, he set his own conditions. It was a symbolic ceremony. Nothing real was to come out of it.
But, it was enough for Ma'moon, who ordered the announcement of the great news throughout the Muslim homeland and called people to give pledge of allegiance to the Imam.

The ceremony of giving the pledge of allegiance to Imam al-Reza(A.S.)
was conducted before a multitude of people, the size of which was unprecedented in Islam. After the ceremony, Ma'moon asked Imam al-Reza(A.S.) to deliver a speech to the people.
Imam al-Reza(A.S.) rose up, and in a few, eloquent words, he explained his position toward the existing authorities, and showed that he could not bridge the gap between himself and the ruler. He said, after praising Allah:
"We have a right over you, as we are the progeny of the Messenger of Allah (S.A.W.). As he is your honour your obligation towards us, we will certainly do the same for you."
This address, of the Imam(A.S.) is the testimony of his mistrust for the future of the covenant. In it, he alludes to his doubts by saying, "Should you honour your obligation towards us, we will certainly do the same for you."

Sheikh Mufid quotes Mada'ini as having said: "When Imam al-Reza(A.S.)
took his seat at the celebation made to confer the post of "heir apparent" on him by Ma'moon, speakers and poets took turns praising him and showing their happiness on the occasion. Standards fluttered overhead. A cloce companion of Imam al-Reza(A.S.), who was present, related: 'I was sitting beside him on that day. He looked at me. I was very happy at what had taken place. He beckoned to me to draw near him and I did.'Do not bother with this matter,'he said under his breath lest someone hear us, 'Do not rejoice at it. It is something that will never be realized.'"
The caliph, Ma'moon was not that person who refrains himself from the world's pleasures, including power. He killed his borhter, Amin, for the sake of power and killed those who served him or those who served his father, Rasheed, such as Tahir bin Hussein, Fadl bin Sahl, and others who participated in executing the plans of Ma'moon in establishing his authority. It was only natural that Imam al-Reza(A.S.) would meet the same fate because he was more dangerous, in the eyes of Ma'moon and his inner circle, than any other man at that time. Added to that was the infighting, the false reports and the attemmpts to distort the image of Imam al-Reza(A.S.)
in the Abbasid palace.
History tells us that Ma'moon put poison into some fruit (pomegranates) which was presented to Imam al-Reza(A.S.), and, thus, he martyred the Imam (A.S.).
Ma'moon felt the situation would be very grave for himself, and the reaction of the descendants of Ali (A.S.), and the masses of the umma, would be very violent of he were to be accused of murdering the Imam (A.S.).
Historians have it that people immediately pointed an accusing finger at Ma'moon. They blamed him, directly, as the murderer of the son of the Prophet of Allah (S.A.W.). People buzzed with the news of the Imam's martyrdom, particularly around the house where the body of the Imam(A.S.) was laid. Fearing a massive reaction on the part of the people, for it was a good opportunity that could be seized to stir up people's feelings, Ma'moon asked Muhammad, son of Ja'far, the paternal uncle of Imam al-Reza(A.S.) to go that the funeral of the Imam(A.S.) would be postponed.
Thus, Imam al-Reza(A.S.) departed for ever, reciting this verse, the last words he had said:
"Say:Had you remained in your houses, those for whom slaughter was ordained would have gone forth to the places where they would be slain."
That was on the last day of the month of Safar 203 A.H., in the city of Toos; its modern-day name is Mashhad.