Was Ali ibn Abi Talib infallible, as the Shiites claim, in that he never committed any errors in his life?

The Companions, may Allah be pleased with them, are the best of the Ummah, but they are not infallible. The Shia belief in the infallibility of Ali and all their twelve Imams is a false belief, to the extent that they claim their infallibility from forgetfulness, which has not been proven even for the prophets. Attributing infallibility to a person means attributing prophethood to them, because the infallible must be followed in everything he says, and this is exclusive to prophets. By doing so, the Shia have elevated their Imams above the prophets; in fact, they have equated them with the Lord of the Worlds, as explicitly stated by Khomeini when he said, "The teachings of the Imams are like the teachings of the Quran."

The Shia claim that Ali never made any mistake is incorrect. He regretted things he did, and he had fatwas and interpretations that contradicted the authentic Sunnah, such as his opinion regarding a pregnant woman whose husband died, that her waiting period (iddah) extends to the longer of the two terms, whereas the Sunnah dictates that she becomes lawful upon delivering her pregnancy. Al-Shafi'i and Muhammad ibn Nasr al-Marwazi collected many of Ali's sayings that were abandoned because they contradicted textual evidence, unlike Abu Bakr al-Siddiq, for whom no fatwa or ruling contradicting a text is known.