MA'SUM

The word ma'sum is derived from the verb asama, means prevented, hindered, protected, defended, preserved, etc. Hence, ma'sum means one who is incapable of error and sin. In Islamic theology, the Arabic term isma both impeccability and closely related notion of infallibility, which is not an inherent quality, but rather a divine gift bestowed on the Prophets and Imams.

See Immunity of Prophets and Immunity of Imams