Ashari school position is they are infallible in small and great sins. Some ayats of Quran and hadith seem to imply they are not. How are these interpreted by classical scholars? And what proves the Ashari position?
See: “Infallibility of Prophets (عصمة الأنبياء`Ismat al-Anbiya)” at sunnah.org.
Among the points made:
The infallibility of the Prophets is an established fact based on reason and tradition.
Reason requires the infallibility of the Prophets, upon them all be peace, because:
[Firstly]…the Prophets came to convey to people the Message of God. If we liken this Message or the Divine Revelation to light or pure water, as the Qur’an itself does (al-Ra`d, 13. 17; al-Nur, 24.35), it is absolutely necessary and indispensable to the nature of the Revelation that both the Archangel Gabriel who brought the Revelation, and the Prophet himself who conveyed it to people, should be absolutely pure. Otherwise, that Divine light, the Revelation, would have been extinguished or dimmed, or that ‘pure water’ polluted. … This is clear from the following verses of the Qur’an:
O Messenger! Convey what has been sent to you from your Lord. If you did not, you would not have fulfilled His mission. And God will defend you (ya`simuka) from people. Certainly, God guides not the unbelieving people. (al-Ma’ida, 5.67)
Secondly, people learn from the Prophets all the commandments and principles concerning belief and conduct. In order that people should learn these commandments in their pristine purity and truth and as perfectly as possible to secure their happiness and prosperity in both worlds, the Prophets must, first, represent, and, then, present them without any faults or defects, for they are guides and good examples for people to follow, as explicitly stated in the Qur’an:
You have indeed in the Messengerof God a beautiful pattern, an excellent example, for anyone who aspires after God and the Last Day, and who engages much in the remembrance of God. (al-Ahzab, 33.21)
Thirdly, the Qur’an commands believers to obey all the orders or prohibitions of the Prophet without exception, and emphasizes that:
it is not fitting for a believer, man or woman, when a matter has been decided by God and His Messenger, to have any option about their decision (al-Ahzab, 33.36).
It also warns believers that what falls to them when God and His Messenger have given a judgment is only to say, ‘We have heard and obeyed’ (al-Nur, 24.51). Absolute obedience to a Prophet means that the Prophet is right in all his commands and prohibitions.
Tradition also proves the Prophets’ infallibility.
God says in the Qur’an concerning the Prophet Moses:
I cast love over you from Me (and made you comely and loveable) in order that you might be brought up under My eye. (Ta Ha, 20.39)
The Prophet Moses, upon him be peace, was brought up by God Himself and prepared for the mission of Messengership. Therefore, it is inconceivable that he may have committed a sin at any time in his life.
The same is true of all the other Prophets. For example, God’s Messenger, upon him be peace and blessings, says of Jesus: Satan could not touch Jesus and his mother at his birth. Jesus was protected from birth until his elevation to the Presence of God.
…Jesus, like all the other Prophets, was protected from all kinds of sin from his birth. God’s Messenger, upon him be peace and blessings, intended in his childhood to attend two wedding ceremonies at different times but, on each occasion, he was overpowered by sleep which prevented him from attending.
[In sum] …All the Prophets were infallible. They never committed a sin, minor or major, and their lives were spent doing virtuous deeds.