Is there a single sahih hadith in the Sunni hadith corpus which proves the Ibn Saba "starter of Shi'ism" tale to be true?
(i)– Amr bin Marzooq narrated to us, he said: Shu’ba told us, from Salama bin Kuhail from Zaid bin Wahb, he said: Ali said: What do I have to do with this black container? He meant: Abdullah bin Saba’ and he used to attack Abi Bakr and Umar. This is what Salama said, from Zaid bin Wahb.
(ii).– Muhammad bin Abbad Al-Makki said: Sufyan narrated to us, he said: Abd Al-Jabbar bin Abbas Al-Hamadani narrated to us, from Salama, from Hujayyah Al-Kindi, he said: I saw Ali on the pulpit saying: Who will excuse me from this black container that lies upon Allah! He meant: Ibn Al-Sawda’.( Al-Tareekh Al-Kabeer 3/177 ) ; {Online Source}
(iii). Abu Ishaq Al-Fazari narrated from Shu’bah from Salamah b. Kuhayl from Abu Al-Za’raa’ AND from Zayd b. Wahb that Suwayd b. Ghaflah entered upon Ali during his rule, and said, “I passed by a group who were mentioning Abu Bakr and Umar, claiming that you hold the same views towards them both. Among them was Abd Allah b. Saba, and he was the first to manifest that. So, Ali said, “What does this evil black man want from me?” Then he said, “I seek Allah’s refuge. My opinion of them both (i.e. Abu Bakr and Umar) is nothing but good and beautiful.” Then he sent a messenger to Abd Allah b. Saba and exiled him to al-Madain, and said, “He shall not live in the same town as me ever again.” Then he rushed to the pulpit and gathered the people, and delivered a long speech to praise them both (i.e. Abu Bakr and Umar). At its end, he said, “Verily, if it reaches me that anyone places me above them both, I will whip him with the whipping of a lying slanderer.”(Lisan al-Mizan of Hafiz ibn Hajar Asqalani, vol 3, page 290, #1225).
We find two of the earliest and most reliable Shia historians – Al-Hasan bin Musa Al-Nawbakhti and Sa’ad bin `Abdullah Al-Qummi. Together, they describe the formation of the Saba’ee sect (the followers of Ibn Saba’) :
“A group of scholars from the companions of Ali (alaihi alsalam) said that Abdullah bin Saba was a Jew, who converted to Islam, and befriended Ali (alaihi alsalam), and he used to say, as a Jew that Yusha’ bin Noon is after Musa (alaihi alsalam) with this view, and so he said in Islam after the death of the Prophet (salallahu alaihi wa aalih) about Ali the same (belief). He was the first to say that it is mandatory that Ali (alaihi alsalam) was the Imam, and the first to disassociate from his enemies, and he made takfeer of them. It is in this light that those there were against the Shias said: The origins of Rafdh are taken from Judaism.” (Firaq Al-Shia .p. 32)
It is sufficient for Ahl Al-Sunnah to simply establish the existence of the man, who wasn’t from Ahl Al-Bayt, that had views that evolved into modern day Shiasm. Refer to Firaq Al-Shia by the top Shia classical historians Sa’ad Al-Ash’ari and Al-Nawbakhti. They have stated clearly that there is a sect called the Saba’ee sect and that they are the followers of Ibn Saba’. They also include that they are the first exaggerators, and that Ibn Saba’ used to curse Abu Bakr and `Umar, believe in Raja’ah, believed in Imamah, and was originally a Jew.