Al-Kashshi mentioned that Yousuf bin as-Sakht said, ‘Ali bin Ja’far was one of the deputies of Imam al-Hadi (a.s.). One day, he was betrayed near al-Mutawakkil who threw him in prison. He remained in prison for a long time and he could not bear longer. Therefore, he asked an agent of the Abbasid government to intercede for him to be set free and he would give him three thousand dinars for that. The agent went to Ubaydillah, who had a good position near al-Mutawakkil, and asked him to intercede with al-Mutawakkil for Ali bin Ja’far. Ubaydillah responded to him and interceded with al-Mutawakkil to set Ali bin Ja’far free, but al-Mutawakkil refused and said to him, ‘If I doubted you, I would say you are a Rafidhi (Shia). This is a deputy of Abul Hasan al-Hadi and I have determined to kill him.’
Ubaydillah regretted his intercession and told his friend (the agent) that al-Mutawakkil had determined to kill Ali bin Ja’far and there was no chance for setting him free. Ali bin Ja’far became so distressed and wrote a letter to Imam al-Hadi (a.s.) saying to him, ‘O my master, please do something for me! I fear I may lose my faith.’ Imam al-Hadi (a.s.) replied to him, ‘Since the matter has reached this point with you, I will pray Allah for you.’
Al-Mutawakkil became seriously ill and his fever increased. Therefore, he ordered his men to set free all prisoners and gave a special order to set Ali bin Ja’far free. Al-Mutawakkil ordered Ubaydillah to set Ali free and to beg him to forgive him (al-Mutawakkil) what he had done to him. Ali was set free and went to live in Mecca as Imam al-Hadi (a.s.) had ordered him.( Rijal al-Kashshi.)