Merv is the name of a city in Khurasaan. After Imam Kadhim's death, Imam Ridha (A.S.) assured the office of the Imamate. He was 35 years old. He was now the protector of Islamic Ummah and the guide of the Muslims. He was the only successor who was given this responsibility by his father Imam Musa al-Kadhim (as). He was also the guardian of his children after his death.
The oppression and the cruelty of Harun's rule went on but Imam Ridha (A.S.) continued with the responsibility of carrying out divine duties and went on spreading the word of God and the rights without any fear. He was always busy and never rested until he reached his aim.
Harun could not bear to watch Imam becoming so popular and his followers adoring him but he could not openly show his enmity or do anything to stop the Imam.
Finally in 193 (A.H.), Harun became sick and died. By his death the Muslims were relieved of one of the most evil oppressor and his tyranny.
After Harun, his brother Amin became the Caliph. He ruled for only 4 years, as there was bitter fighting between Amin and his brother for the Caliphate. This led to bloodshed and Amin was subsequently killed in the year 198 (A.H.), after which Mamun became the ruler.
It was during this time when the 2 brothers were fighting that Imam Ridha (A.S.) made the most use of this opportunity to spread the word of God and guide the Muslim Ummah.
The Abbasid government at this time was busy fighting amongst themselves for the kingdom, so there were fewer hardships for the Imam's family.
Mamun with his trickery came to power. He was not a Caliph who was just but someone who had fooled his people to get the power. This deceiving continued and to show that he was not only a wise king but also a man who encouraged intellectual and scientific education. He invited scholars, learned men, organized meetings, and seminars. So on one side he supported the scholars and on the other side, to attract the many Muslims, he openly showed the love he had for Ahlul bayt, started praising Imam Ali and cursing Muawiyah. This was a concerted effort to trick the Shias that he also was interested in the spread of Islam through the region. His supporters were not happy with his strategy but Mamun knew that if his enemies and the Shias would get together then he would be overthrown so he had to take first the Shias into his confidence and to do this he devised a plan to offer Imam Ridha (A.S.) to be the successor after him. This was to win confidence from both the enemies and the Shias.
So Mamun started writing letters upon letters to Imam Ridha (A.S.) to become his successor. But despite all the forces of Mamun it did not bear fruit as Imam Ridha refused to take their responsibility, which would be harmful for Muslims, so he bluntly refused. But Mamun was not going to give up so easily when he realized that his plan was not working he sent a man called Raja bin Dhahhak to Medina in 200 (A.H.) with an order to bring Imam to Merv (later called Toos and now Mashad). This was at that time the seat of his empire and he hoped the Imam would agree to be the governor of this city.
On receiving the information the Imam visited the grave of the Prophet and the Imams (buried in the Jannat-ul-Baqi) and said goodbye to his children, brothers and sisters including Fatimah Ma'soomah and left Madina for Merv. There was a sad atmosphere as the whole family was unwilling to see their protector and guide leave them but had no choice.
For Fatimah Ma'soomah this separation was very difficult as after the passing away of her father, the 7th Imam she was continuously under the guardianship of her brother Imam Ridha (A.S.). Now he had to leave Madina and for her the happy days were over.
Mamun had devised a plan for the Imam's journey. He had made sure that on Imam's route to Merv the Imam's caravan should not pass the two towns of Shias, which were Kufa and Qum. He was afraid that if the Imam passed these places there could be a revolution and he would be overthrown.
He also knew that the Shias of Kufa and Qum had a great love for the offspring of the Prophet. So the Imam should under no circumstances take this route.
The Muslim population however made all arrangements for the Imam to welcome on the route he was supposed to pass and took full advantage of the Imam's presence when the caravan stopped.
The whole route of Iran was decorated and he was warmly welcomed. One of the towns on the route to Iran was Neshapur. When the people of Neshapur heard that the Imam was coming they gathered and were anxious to learn something from the Imam. When Imam camped, the people gathered at his camp and asked Imam to teach them something and the Imam agreed. He told them a Hadith of the Prophet (S.A.W.). He said, LA ILAHA ILLALLAH is a strong fort and whosoever enters the fort will be saved from the fire of Hell. Then the Imam moved a few steps forward and continued with the Hadith and addressing, the crowd said "but there are conditions to it and I am one of those conditions". Imam was actually emphasizing the importance of Imamate by this Hadith, and teaching them that only belief in Allah is not sufficient for the passage to heaven.
After a few days in Neshapur, Imam went on with his journey to Merv. Mamun again requested the Imam to be his successor but Imam as before refused. This arrangement between Mamun and Imam continued for two months and with Mamun's force Imam had no choice. So on the 7th of Ramadhan 201 (A.H.) tearfully and sadly he agreed but with a condition that he would not involve himself into day to day deliberation of the government.
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