Imam Ali al Retha
Imam Ali al-Retha (a.s) was 35 years old when he became an Imam after his father died in prison of Harun al-Rashid in Baghdad. At that time Harun Al-Rashid was the absolute ruler of Baghdad and he made life very difficult for the Imam (a.s) and his followers.
Harun Had two sons, one called Mamun from a Persian mother and one called Amin from an Arab mother. The half-brothers did not get along and each one wanted to be the Caliph. Harun therefore decided that after he died, Mamun would rule the Persian kingdom and Amin would rule the Arab kingdom. However after he died in Persia (modern day Iran), Mamun became busy with the burial of his father and Amin took that chance to say that
he was the ruler of all the Kingdom.
This left Mamun very angry and seeking revenge. Mamun knew that most of the Persians loved the Ahlul bayt and their teachings so decided that if he convinced them that the Imam was on his side, that the Persians would become loyal to him and not his brother. The plan he came up with was that he would force Imam al Retha (a.s) to live in Tus (an ancient city in Mashhad, Iran) with him and that he would pretend to respect the Imam (a.s) and say that the Imam was to be his successor.
Imam Retha (a.s) was therefore ordered to travel to Persia and once he was there Mamun told him that he wanted him to be his successor. The Imam (a.s) knew the plan Mamun had so he did not accept until he was left with no choice. Once the Imam (a.s) accepted Mamun announced to the people of Peria that the Imam of their time was on his side that he was to be his successor. Sure enough his plan worked because the Persians finally became loyal to him.
With the help of the Persians, Mamun's army invaded the capital of the Abbasid empire, Baghdad, Amin was killed and Mamun become the sole ruler of the Abbasid Empire. Although Mamun did not like the Imam (a.s), he kept him alive as he still did not feel confident that he had total control of his empire.
In the mean time, Imam Retha (a.s) was able to share his knowledge to the public through his lectures and conferences. One example is when Mamun's Prime Minister Fadl ibn Sahl arranged a conference on religions. He invited the leaders of different relgions, including Zoroastrians and Christians and Jews to hear what the Ahlul Bayt had to say to impress them of their spiritual abilities and excellences. It was in these discussions with leaders of other faiths that the Imam clarified the position of sinlessness of the Prophets (a.s) and of the guided Imams (a.s).
The Imam (a.s) had an amazing abilty to move people towards true worship for Allah, and this in turn made them loyal and respectful of him.
On one such occasion Imam Retha (a.s) was asked by Mamun to lead Eidul Fitr prayers at the end of Ramadan. First the Imam (a.s) declined, but when Mamun insisted, he agreed on the condition that he will direct the occasion as he would deem fit.
On the morning of the Eidul Fitr the military and civil leaders assembled outside the door of the Imam (a.s). When he came out they were surprised to find him bare foot, wearing a white shirt and white headgear and his companions to followed him in the same manner. He came out on the Road to the mosque outside the city of Merv.
All the people who saw the Imam (a.s) in this fashion copied him and they all walked barefoot. Even the military chiefs and civil judges walked bare foot and soon there was a huge crowd following the Imam (a.s). He was saying Takbir loudly and all were following him and shouting Takbir (God is great).
The crowd became so spiritually intense that Mamun was informed of this huge crowd following of the Imam (a.s) and he immediately asked the Imam (a.s) not to lead the Eid prayers. He did not want the people to feel so enthusiastic about the Imam (a.s) or prayer in case they start to realise that he was not at all important.
Imam Retha (a.s) was eventually poisoned by Mamum as soon as he gained full control over the Abbasid empire.
The Imams (a.s) were perfect examples of kindness, mercy and faith and wherever they went people loved them.
The people of Tus loved Imam Retha very much and therefore Mamun tried to gain their support by making Imam Retha (a.s) his heir. As soon as he no longer needed the Imam, Mamun killed the Imam (a.s).