He also propagated this point that the Prophet's immediate...
He also propagated this point that the Prophet's immediate guardian and successor was 'Ali ibn Abi Talib whose right of caliphate had been usurped by 'Uthman. 'Abd Allah ibn Saba' pretended to incline to and support 'Ali. A number of the Prophet's companions and other Muslims were taken in by him and believed his words.
'Ammar ibn Yasir, Abu Dharr, Abu Hudhayfah, Muhammad ibn Abi Bakr, Malik al-Ashtar, Hujr ibn 'Adi and others who were the most famous of the Prophet's companions and their dependents followed and gathered around him. Thus that mysterious Jew managed to win the attention of these exalted men and formed a party known as the Saba'is and it was the members of this group of companions and Muslims who besieged 'Uthman in his house and killed him.
So in Sayf ibn 'Umar's imagination, the Jew, 'Abd Allah ibn Saba', cunningly entered the Muslim ranks, pretended to love and support 'Ali, formed a party of Saba'is consisting of the Prophet's companions and other Muslims and eventually killed their caliph.
Sayf ibn 'Umar in the same fable continues to narrate the historical events subsequent to 'Uthman's assassination down to the battle of al-Jamal, and then with his imaginative brain he created another character in addition to 'Abd Allah ibn Saba' and named him al-Qa'qa' ibn 'Amr, and made him a companion of the Prophet 172 and gave him the mission of mediation and peace making, and then continued his fable as follows: In the battle of al-Jamal al-Qa'qa' ibn 'Amr tried hard to establish peace, sometimes by contact with 'Ali, and on other occasions with 'A'ishah, Talhah and az-Zubayr, inviting them to peace and tranquility and warning them of war and bloodshed.
At last al-Qa'qa' succeeded as a dove of peace to win the agreement of the commanders of both armies to establish peace between them and so once more silence and tranquility reigned over both camps. The Saba'is, namely 'Abd Allah ibn Saba', and his followers, were worried about the consequences of this peace and vexed at the disruption of their destructive schemes. So one dark night they gathered together for discussion and prepared plans for ending that peace.