Ismah

‘Iṣmah or ‘Isma (Arabic: عِصْمَة‎‎; literally, "protection") is the concept of incorruptible innocence, immunity from sin, or moral infallibility in Islamic theology, and which is especially prominent in Shia Islam. In Shia theology, ismah is characteristic of prophets, imams, and angels. When attributed to human beings, ismah means "the ability of avoiding acts of disobedience, in spite of having the power to commit them". Along with a pure constitution, excellent qualities, firmness against opponents, and tranquility (as-Sakinah), ismah is a divine grace bestowed by God.

An infallible (Arabic: معصوم‎‎ ma`sūm) is someone who is free from error in leading people to belief, in perceiving divine knowledge, and in practical matters. Prophets must be immune from all errors and sins in order to perform their mission of upholding and promoting the divine religion, interpreting the Qur'an, and establishing a wholesome social system.

The Qur'an's verse of purification implies that God purifies only the Ahl al-Bayt from any kind of sin, error, and defilement in their creation. Both Shia and Sunni hadith state that Ahl al-Bayt refers only to the People of the Cloak and does not include the wives of the Islamic prophet Muhammad.

According to Twelver Shia, The Fourteen Infallibles (Arabic: معصومون‎‎ Ma‘ṣūmūn) "divinely bestowed free from error and sin" include Muhammad, his daughter Fatimah, and the Twelve Imams.Ismaili also attribute ismah to Ismaili imāms and Fatima Zahra, daughter of Muhammad, while Zaidis do not attribute the quality to the Zaidi imams.

...
Wikipedia