One day the Abbaside Caliph Mamun asked Imam Ridha’ (a.s): Mamun: Do you believe in the infallibility of the Prophets? Imam: Doubtlessly Mamun: But the Holy Quran itself says regarding Adam (a.s): Adam disobeyed his Lord and then he became misguided. This clearly shows that Adam was a sinner. Imam: It was Allah’s command that: O Adam, you and your wife, both remain in Paradise and eat whatever you like but do not eat from that tree or of its same kind. He did not eat from that tree; rather it was Satan who instigated him to eat from another tree of the same kind.
The Satan told him, “Allah has forbidden you to eat from this particular tree and not from other tress of the same kind.” Then Satan also took a false oath. Since Adam and Hawwa had never seen anyone taking a false oath before this, they were befooled. And trusting this oath they committed that act. And Adam performed this thoughtless action even before he became a prophet.
It was not a greater sin that he should become deserving of Hell. It was merely a case of giving up a preferable option (Tark-e-Awla). Or it was a detestable act (Makruh), which is acceptable from prophets before receipt of divine revelations.
When Allah appointed him as a prophet, he was infallible. He did not commit either a greater or a lesser sin. Mamun: All right. What do you say regarding Prophet Ibrahim? The Quran mentions in clear words: “When the darkness of the light spread on him he saw a star and said: This is my Lord.” Is this not obvious polytheism, that a star should be addressed as ones Lord? Imam: The phrase: “This is my Lord” is interrogative which means; “Is this my Lord?” Since the people of that time were star-worshippers and their belief had reached his ears, thus when he came out of the cave and saw the stars he asked by way of question: Is this my Lord? Thus when it disappeared, he said: I do not like those who disappear. That is, this cannot be a quality of my Lord. It is a quality of a creature. When the moon arose, again he asked in a negative interrogation: Is it my Lord. In the same way he mentioned this for the sun. Thus whatever he said was against the falsehood of the star-worshippers and not regarding his own beliefs.
Mamun: O son of the Messenger of Allah (S)! May Allah give you a good recompense. You have given a very good reply. But there remains a slight misgiving in the heart. The Almighty Allah says in the Quran: “Ibrahim said: Show me how You enliven the dead. He said: Don’t you have faith (in it)? He said: yes, but that my heart should be satisfied.” So, tell me, did the Khalil (friend of Allah) not have faith in the power of Allah before this?
Imam: The Almighty Allah revealed upon Ibrahim (a.s) that I will make a righteous slave of Mine as the Khalil. And if he asks Me to enliven the dead for him, I will fulfill his desire. So, Ibrahim was uncertain whether, he was that Khalil or someone else. That is why he said thus. That is, he desired certainty of the heart for this matter.
Mamun: May Allah recompense you! You have removed this objection in a beautiful manner. Now, there is one objection regarding Prophet Musa (a.s). It is that Musa (a.s) said: My Lord! Show Yourself to me so that I can see You. This shows that Prophet Musa did not even know that ones eyes could not see Allah.
Imam: It is not so. Musa (a.s) well knew that He is not visible to the eyes. But his people were insisting that he should pray to Allah to show Himself to him. “We will not bring faith in Him without seeing Him with our eyes.” Thus, becoming helpless of his people he prayed to Allah in the same words, that the people insisted. Thus this request of Musa was on behalf of the people.
Mamun: It is mentioned about Yusuf (a.s) that: She intended with him and he intended with her. If Yusuf was a prophet how can he have such intention?
Imam: You have not recited the complete verse, which is as follows: Yusuf would also have intended if he had not seen the proof of his Lord. Since he was an infallible prophet, he did not make such an intention. Another meaning of this is that Zulaikha made an intention of sin, and Yusuf (a.s) made an intention “not to do it”.
Mamun: All right. It is mentioned about the Messenger of Allah (S) in the Quran: Indeed We gave you a clear victory so that Allah may remit your past and future sins. This shows that the prophet was a sinner.
Imam: This verse does not denote the sin of the Prophet. Rather it means that: O Prophet! Your denouncement of the idols of the polytheists and your invitation towards the oneness of God, which were sinful actions in the eyes of the people, now that Mecca is conquered, and people willingly or unwillingly have become Muslims, thus all your past actions (sins in the view of the polytheists) are forgiven. That is, you are no more a sinner in their view.
Mamun: Son of the Messenger, I am thankful to you that you removed all my doubts.
Reference :Akhlaq al-A’imma, Morals & Manners of the Holy Imams