Hence the next dynasty to rule the Muslim world was known as...
Hence the next dynasty to rule the Muslim world was known as Banu ‘Abbas or the ‘Abbasids. Hisham, the Umayyad caliph, had ordered the sixth Imam to be arrested and brought to Damascus. The later Umayyad rulers were not strong enough to harass the Imam. The Imam was then arrested by Saffah, the first ‘Abbasid caliph and brought to Iraq. After some time, he was allowed to return to Medina. The reign of Mansur, the second ‘Abbasid caliph, was even worse for the Shi’as.
He ordered such torture and merciless killing of many of the descendants of the Prophet who were Shi’ite that his actions even surpassed the cruelty and heedlessness of the Umayyads. At his order they were arrested in groups, some thrown into deep and dark prisons, and tortured until they died, while others were beheaded or buried alive or placed at the base of or between walls of buildings, and walls were constructed over them.
Once Mansur wrote to Imam as-Sadiq (a.s.) asking him why he did not visit him like other dignitaries. The Imam wrote in reply: “Neither do we possess any worldly treasure for which we may fear you, nor do you possess any spiritual virtue for which we may seek your favour. So why should we come to you?” Mansur replied, “Then come for admonishing us.” The Imam replied, “Those who seek this world will never admonish you, and those who seek the hereafter will never come to you.” 5.
Last Days & Death Finally, Mansur had Imam as-Sadiq (a.s.) arrested and brought to Samarrah (Iraq) where he had the Imam kept under supervision, was in every way harsh and discourteous to him, and several times thought of killing him. Eventually the Imam was allowed to return to Medina where he spent the rest of his life under severe restrictions placed upon him by the Abbasid ruler, until he was poisoned and martyred through the intrigue of Mansur.
Upon hearing the news of the Imam’s martyrdom, Mansur wrote to the governor of Medina instructing him to go to the house of the Imam on the pretext of expressing his condolences to the family, to ask for the Imam’s will and testament and read it. Whoever was chosen by the Imam as his inheritor and successor should be beheaded on the spot. Of course, the aim of Mansur was to put an end to the whole question of the imamate and to Shi’ite aspirations.