If the prophets were subject to errors, flaws or sin, they might on some occasions misguide men instead of guiding them, which is against the divine mission of mercy and grace. If  in everything that a prophet said or did there were a possibility of his being right or wrong, it would be impossible for us to follow him. The result would be that a prophet would be seen as an ordinary being, and the benefit of  his mission would be completley lost

A manu…/A.Naqavi/p:8