If he asks, “How did they come to agree upon killing him?” he is told: It began with a certain Jew called Ibn al-Sawdā’, also known as Abd Allah ibn Saba—may Allah’s curse be upon him—who claimed to have embraced Islam and settled in Medina. His envy of the Prophet—peace and blessings be upon him—his Companions, and Islam drove him to embed himself among the Muslims, just as the king of the Jews, Paul ibn Shāwidh, embedded himself among the Christians until he led them astray, divided them into sects, and caused them to become rival factions. Once affliction and disbelief had taken firm root among them, he abandoned them—though his story is lengthy—and subsequently reverted to Judaism.
Likewise, Abd Allah ibn Saba outwardly professed Islam and championed the commanding of right and forbidding of wrong. He acquired followers throughout the various regions. He then began openly impugning the governors, followed by Uthmān—may Allah be pleased with him—and then Abu Bakr and Umar—may Allah be pleased with them both. Thereafter, he professed devotion to Ali—may Allah be pleased with him. Allah the Generous preserved Ali ibn Abī Tālib, his children, and his descendants—may Allah be pleased with them—from the doctrine of Ibn Saba and his followers, the Saba’ites.
When sedition and error became firmly entrenched in Ibn Saba and his followers, he went to Kufa and acquired followers there. He then traveled to Basra and acquired followers there, after which he went to Egypt and acquired followers there. All of them were people of error. They then agreed upon an appointed time and corresponded with one another so that they might gather at one place and then proceed together to Medina to stir up sedition in the city and among its people. They did so, then marched to Medina and killed Uthmān—may Allah be pleased with him. Despite all this, the people of Medina remained unaware until the conspirators arrived among them.