The Principal Duties of Islam: The Isma Doctrine by John Gilchrist
1. The Development of the Isma Doctrine. Throughout the Muslim world today it is generally believed that all of the prophets enjoyed an isma, a protection against sin, and that they were accordingly sinless. It is one of the anomalies of Islam that this Doctrine has been established and maintained against the plain teaching of the Qur'an and Hadith to the contrary. The orthodox belief is that the prophets do not commit sin, and are sinless (ma'sum), [...]