Imam Reza's (A.S.) Journey from Medina to Marw
In the year 200 A.H./ 816 A.D., Mamun sent his maternal uncle Reja bin Zahhak from Marw to Medina with flattering letters of invitation for Imam Reza (A.S.) and a group of other Alavis and revolutionaries, to come to Marw. He also gave instructions to his uncle to show the utmost respect to Imam Reza (A.S.) and invite him to Khorasan.
Imam Reza (A.S.), being aware of Mamun's real intentions and the outcome of his journey to Khorasan, initially declined the invitation politely. But, following Reja's continuous insistence and taking into account the affairs of Muslims, the Holy Imam had no other choice but to reluctantly accept Mamun's invitation.
The Holy Imam bade farewell to the holy shrine of his grand father, the Holy Prophet of Islam(S.A.W.) in a highly emotional state.
Before departure from Medina,Imam Reza (A.S.) gathered his companions and other members of the Holy Prophet's Household, and told them that his young son, Muhammad Taqi al-Jawad (A.S.), was his successor after him and should be obeyed in all matters(Ibn Shahr Ashoub in Manaqeb and al-Masoudi in Asbaat al-Wasiya). Regarding the succession to the Imamate in childhood by the ninth Holy Imam,Muhammad Taqi al-Jawad it is interesting to note that Shaykh Mufid has recorded the following account in his "Kitab al-Irshad".
"I (Safwan bin Yahya) said to Imam Reza (A.S.): ... We ask Allah never to show us the day (of your death) but if something happened, to whom (will the Imamate belong)? He (the Holy Imam) pointed out to Abu Ja'far (his son, the future Imam Jawad) with his hand while he was standing in front of him. I said: May I be your ransom, this is a child of three years old! That does not harm him, he (the Holy Imam) replied Jesus(A.S.) gave evidence (of his mission) when he was less than three years old."

Towards Khorasan
Imam Reza(A.S) did not take any member of his household with him to Marw.His Holiness intended to make the people aware of the exile that Mamun had planned for him. According to Mamun's commands the direction of Imam Reza's(A.S.) caravan from Medina to Marw was predetermined.
Mamun, in his letter to Imam Reza (A.S.), told him not to plan his journey to Khorasan via the cities of Kufa (in Iraq) and Qom (in north-central Iran), because he dreaded the idea of Shi'ites getting in touch with the Holy Imam and asking him to abandon his journey.
Imam Reza (A.S.) left Hijaz for Iraq and after passing through Basra, he travelled by ship to the port known as Khorramshahr today, and from there he went t Ahwaz. His route next lay through the central Iranian cities of Isfahan and Yazd. From there he went to Tabas, and after passing the Ahuwan region and Miyame, he entered the ancient city of Neyshabur.
Ma'mun, the cruel and cunning Abbasid caliph in the year 201 A.H./ 817 A.D. forcefully exiled Emam Reza (A.S.) from Medina to Marw. (The city where Mamun's seat of caliphate was located).
According to Ma'mun's commands the direction of Emam Reza (A.S.) caravan from Medina to Marw was predetermined. Holy Emam (A.S.) had to pass through some towns and villages. He arrived in Marw on the 10th of Shawwal in 201 A.H./ 1 May 817 A.D., via Basrah, Khorramshahr, Ahwaz, Rey, Neyshabur, Sanabad and Sarakhs. Throughout his long journey, the Holy Emam (A.S.) was cordially received by the people living in those cities and villages on the route.
The most interesting incident during the journey occurred in Neyshabur. The great metropolis of Neyshabur, during that time was one of the most important and leading centres of Islamic learning, where large number of jurisprudents and scholars of Hadith were residing in that city.
The day His Holiness was sitting in a litter placed on a mule and passing through the avenues in Neyshabur, throngs of peolpe estimated more than 120.000 earnestly gathered round his retinue, and there thousands of distinguished scholars and traditionists present among the crowd requested the Holy Emam (A.S.) to narrate a Hadith.
Accepting their request His Holiness ordered his men to draw the reins of his mule, and then the Holy Emam (A.S.) drew the hanging curtain of his litter aside. On beholding the holy visage of Emam Reza (A.S.) the witnessing people present there suddenly burst into tears of joy and happily cried out. Some of them tore their robes and knelt to kiss the stirrup of the mule on which the Holy Emam's litter had been placed.

What a public uproar of admiration!!
Nothing could extinguish the fiery applause of the huge multitude assembled there. Then Emam Reza (A.S.), looked at that great congregation and said: Musa ibn Jafar (A.S.), my dignified father once quoted the words of his father Jafar ibn Muhammad Sadiq (A.S.), who in his turn related the words of his father Muhammad ibn Ali (A.S.), who narrated the words of his father Ali ibn Husain (A.S.), who likewise quoted Husain (A.S.), the master of the youth residing in paradise, who directly quoted the Holy Messenger of Allah (S.A.W.), who narrated the words of Gabriel(A.S.), who quoted the divine words of the Exalted Lord as follows:
"There is no God but Allah, the One is My stronghold in which the reciter of this holy verse can enter and then he will dwell there safely, and will not suffer My wrath"
The people who had assembled round the Emam's litter thought that His Holiness' talk was over, but to their amazement the Holy Emam (A.S.) appeared from behind the litter curtain again and added the following words to what he had previously stated:
"But all this depends on some conditions, and I am considered to be one of those conditions".
This historical and the most famous Hadith Qudsi is called "Silsilat al-Dhahab". Emam Reza (A.S.) confirms that worshipping God will be counted as a perfect procedure when it is based on the obedience of the immaculate Holy Emams (A.S.). This historical statement of Emam Reza (A.S.) implied the presentation and assertion of the Emamat (socio-religious leadership) of His Holiness.

Arrival In Sanabad
Imam Reza (A.S.) thereafter left Neyshabur and procceded toward Marw, passing through the place which is known to this day as Qadamgah-since it still bears the footprint of the Eighth Imam(A.S.).
From Dah Sorkh village, he arrived in Sanabad, where he stayed in Humaid bin Qahtaba's palace and saw Harun's grave. On entering the dome, under which lay Harun's remains, the Holy Imam marked a spot with his blessed hand, saying: "I will be buried here, and Almighty Allah will make this place a site of pilgrimage for my Shi'ites (followers) and my friends. By Allah, whoever comes for my pilgrimage and recites salutations (Ziyarah) upon me, will be guaranteed divine mercy and forgiveness by virtue of the intercession of our family (Holy Prophet of Islam's(S.A.W.) Household)."
After two days of stay, Imam Reza (A.S.) left Sanabad for Marw by way of Sarakhs.Throughout his long journey, the Holy Imam(A.S.) was cordially received by the people living in those cities and villages on the route.
On his way to Toos from Dah Sorkh, Imam Reza (A.S.) rested a while at the mountain called 'Kuh Sangi', and as mentioned by Shaykh Sadouq in 'Uyun Akhbar ar-Reza'(A.S.), he prayed to Allah to bless the mountain for the benefit of the local people. He then called for carving a pot from its soft black stone and preparing food in it for him. Today, as any visitor to holy city of Mashhad knows, with the blessings of the Holy Imam(A.S.), pots, utensils and handicrafts, are still made from the soft black stone of Kuh Sangi, which continues to provide a source of income for the local people.

Imam Reza's (A.S.) Arrival in Marw
In Mamun's time, Marw was one of the biggest cities of Khorasan and the capital of the Abbasid caliphate. On Mamun's invitation about 300000 people, among them 33000 partisans of the Abbasids as well as some Hashemites, had assembled in the city to accord a grand welcome to Imam Reza (A.S.), since the caliph had made known his decision to appoint the Holy Imam as his heir-apparent.
Mamun himself, along with his powerful vazir Fazl bin Sahl, and with government officials and troops arranged in ranks went to the outskirts of Marw to welcome Imam Reza (A.S.).
Imam Reza (A.S.) and his caravan entered Marw on 10th of Shawwal, 201 A.H./817 A.D., to a warm welcome from the people who showered him with the customary salutations and 'Salawat' (O' Allah bless Muhammad(S.A.W.) and his pure progeny). The city of Marw was a picture of joy as people celebrated the arrival of Holy Prophet Muhammad's (S.A.W.) grandson in their midst. The whole city was decorated for the occasion.

Successorship to Caliphate
His Holiness was welcomed at Marw by the caliph himself and by Fazl ibn Sahl and some distinguished Abbasid nobles in a place a few leagues outside the metropolis. After some days, Ma'mun offered Emam Reza (A.S.), first the caliphate, His Holiness seriously rejected Ma'mun's proposal. Then Ma'mun proposed Emam to accept the successorship to caliphate, the Holy Emam (A.S.) turned down this proposal also but he was finally forced to accept the successorship to caliphate. The Holy Emam (A.S.) put forward certain conditions that he would not interfere in governmental affairs or in the appointment or dismissal of government agents.

Ritual of Fitr Prayer
In the late Ramadhan 202 A.H. / March 817 A.D., Mamun sent a message to Imam Reza (A.S.) requesting His Holiness to conduct the religious service of the celebration of "Fitr Prayers" (Festival at the end of the month of fasting) in Marw.
The Holy Imam (A.S.) did not first accept that task, but due to Mamun's insistence His Holiness consented to perform the related ritual just on the basis of the method the Holy Prophet of Islam (S.A.W.) used to practice. Mamun accepted Imam Reza's (A.S.) suggestion concerning this issue.
Early in the morning of the celebration day of "Fitr" the horse of the caliph ornamented with glossy galloon was waiting at the gate of the Holy Imam's dwelling place. The high-ranking officials of the state such as military commanders, senior judges, distinguished savants and celebrated authorities of Marw were all in costly costumes waiting to escort His Holiness. Large number of people were waiting here and there, even on the roofs of their houses to visit and welcome the Holy Imam (A.S.).
Unexpectedly His Holiness appeared in plain clothing and bare-footed before that congregation, attended by his own men who were in simple garments and bare-footed. The Holy Imam (A.S.) bare-footed marched forward and glorified God loudly; saying "Allah Akbar" (God is the Greatest of all).
When the officials saw Imam Reza (A.S.) in simple clothing and bare-footed, hurriedly jumped down from the saddles of their horses and tried to take off their boots. The Holy Imam (A.S.) continued glorifying God by repeating the phrase "Allah Akbar" (God is the Greatest of all).
One would probably say an earthquake had unexpectedly occurred in Marw; from every direction the call "Allah Akbar" could be heard, and during his graceful marching the Holy Imam (A.S.) loudly glorified God, and the congregation present there followed His Holiness and shouted "Allah Akbar".
The magnificence and splendour of that demonstration was rapidly related to Mamun, and the rally was reported as an alarm for the caliph. He quickly dispatched one of his men to request the Holy Imam (A.S.) to cease the continuation of that ritual under the pretext of some excuses Mamun had verbally invented. Despite being deeply annoyed Imam Reza (A.S.) , left the place and the people, who had now turned into a fiery mass.

Imam Reza's (A.S.) Prayer for Rain
It happened that soon after the official nomination of Imam Reza (A.S.) as the caliph's successor, there was no rain for quite some time. The enemies seized this natural phenomenon as an opportunity to portray it as an ill omen resulting from Mamuns' declarartion. Mamun, on hearing the rumour became upset, and requested the Holy Imam(A.S.) to pray to Almighty Allah to deliver the people from the drought. The Holy Imam(A.S.) obliged, and on Monday morning with a large number of people, he headed towards the outskirts of the capital city Marw to pray.
Praising Almighty Allah, the Holy Imam(A.S.) started praying for rain. Soon some clouds appeared accompanied by thunder and lightning much to the joy of the people. But the Holy Imam(A.S.) asked them to be patient saying that these clouds were not for them. The clouds passed and were followed by more clouds, also accompanied with thunder and lightning. Imam Reza (A.S.) said that these clouds again were not for Marw but for such and such a place. More clouds followed, and on the eleventh occasion, the Holy Imam(A.S.) said that this time it was for Marw and by the will of Almighty Allah, it would start raining by the time the people reach their houses.
After the people reached their homes, by the will of Allah and the blessed prayers of Imam Reza (A.S.), the downpour started and it rained so heavily that the fountains, ponds, and the deserts were filled with water.

The Holy Imam's (A.S.) Martyrdom
The vicious caliph was scared of the Holy Imam's (A.S.) increasing publicity and popularity. There was a rapid spread of Shi'ism, a growth in the attachment of the populace to the Holy Imam (A.S.). Ma'mun sought to find a remedy for this difficulty and decided to marytr the Holy Imam (A.S.). In 203 A.H./ 818 A.D., Mamun set out for Baghdad and asked Imam Reza (A.S.) to accompany him. At Sarakhs, he assassinated Fazl ibn Sahl, the famous minister and commander of the civil military forces of the Abbasid caliphate.
Imam Reza (A.S.) was imprisoned in Sarakhs by Mamun. Then the Holy Imam (A.S.) was taken to Sanabad and confined in the palace of Humaid bin Qahtabah. During the morning of the last day of the month of Safar 203 A.H./ 818 A.D., the Holy Imam (A.S.) was taken before Mamun in that palace. The caliph, first asked the Holy Imam (A.S.) to eat grapes which were poisoned and then cunningly induced His Holiness to drink venomed pomegranate juice. Mamun in this way wanted not to leave a clue behind that he had poisoned the Holy Imam (A.S.).
The Holy Imam (A.S.) knew everything about that intrigue, and when his companions met him soon after that event, the Holy Imam (A.S.) reported the murderous attempt of Mamun to them.
During that day after saying his noon prayers in seriously ill condition, he summoned one of his private servants and inquired whether the other servants had had their lunch.
"My lord, how can we eat food when we witness you are seriously ill in bed?", answered the man.
On hearing that statement, the Holy Imam (A.S.) asked them to serve the lunch. In that critical condition also he ate some food in the company of his servants and attendants by controlling his severe pain due to poisoning. It was the practice of the Holy Imam (A.S.) to have food in the company of his servants. While having lunch the Holy Imam (A.S.) did not express his severe pain and affectionately talked with each servant of his till all of them completed having their lunch. Suddenly the Holy Imam (A.S.) was seized with intensive pain and languor, and consequently fainted. The holy soul of the innocent Holy Imam (A.S.) departed to heaven and the entire world of faith and sincerity fell into lamentation.
After hearing about the Holy Imam's martyrdom, the people started gathering around Holy Imam's residence and the noise of wailing and crying increased. The mourners considered Mamun as the murderer of the Holy Imam (A.S.).
Being scared of a funeral procession at day time, Mamun contrived to have the burial ceremony done in the dark of night. Caliph ordered his men to inter the holy remains of Imam Reza (A.S.) at the feet of his accursed father Harun al-Rashid,but couldn't,since on all three sides hard rock was found and the only place possible for burial was the spot marked by the Holy Imam (A.S.),above Harun's grave, which was situated in Humaid bin Qahtabah's palace garden. Thus the Holy Imam (A.S.) was buried in the solitude of night at the same place which His Holiness had prophecied during his first visit to Humaid bin Qahtabah's palace at Sanabad in 201 A.H.
Hearing the sad news of Imam Reza (A.S.) martyrdom, De'bel Khozaee, the celebrated Arab poet wrote an elegy in praise and commemoration of His Holiness. The following is a translated theme of the purport of that famous ode:
"Two graves are located in Toos. One belongs to the best man (Imam Reza (A.S.),) while the other is occupied by the worst creature (Harun, Ma'mun's father). This serves as an example for others.
That wicked spirit can gain no benefit from its nearness to the pure body of the Holy Imam (A.S.), and the sacred remains of His Holiness will not be polluted by its foul neighbour."
The holy shrine of Imam Reza (A.S.) is a sacred centre of pilgrimage for the faithful visitors who earnestly and humbly arrive in millions every year in the holy city of Mashhad.
Once a small village called Sanabad transformed into a great metropolis by the presence of the holy shrine of Imam Reza (A.S.).