Ismah

‘Iṣmah or ‘Isma (Arabic: عِصْمَة‎; literally, "protection") is the concept of "impeccability," "immunity from sin", or "infallibility" in Islamic theology, and which is especially prominent in Shia Islam. In Shia theology, Ismah is characeristic 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", as with Prophets and Imams. 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.