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I have seen that Abu Huraira is considered as an unreliable narrator by Shia:
One famous example would be the case of Abu Hurayrah, who narrated over five thousand hadiths: Sunnis consider him a reliable source, Shi'ites do not, and his case is not unique.
Why?
[Not being a Shia myself, if someone sees a mistake here please edit and rectify it].
The Jafaris\Imamis do not consider Abu Hurairah to be a reliable narrator, because they have a narration from Imam Jafar to the effect:
سمعت جعفر بن محمد عليهما السلام يقول: ثلاثة كانوا يكذبون على رسول الله أبو هريرة، وأنس بن مالك، وامرأة
Jafar bin Muhammad said: Three people told lies about the Messenger of Allah: Abu Hurairah, Anas bin Malik and the woman.
بسم الله الرحمن الرحیم
In order to elucidate the issue, of note, there can be diverse reasons/evidences for rejecting him (and in order to prove everyone, there need long discussion and documents... but here I just mention some of the reasons in short, hopefully can help you).
1- His companionship with Ka'b al-Ahbar the Jew, and narrating from him.
2- Him narrating hollow hadiths which usually would convey what the Israiliyyat hadiths (unauthentic and forged hadiths by the Jews or under the influence of them that cause distortion in Islamic tradition, history and tafsir and bring into religion fraud beliefs) conveyed, and in reality, were the Israliyyat themselves.
3- Narrating hadiths that were the opposite of ones narrated by the Sahabas. Imam Ali (as) and Abu Bakr opposing him.
And so on.
Of note, I strived to point out a part of the reasons to reject him, otherwise there can be more reasons to elucidate/persuade it.
Reference:
