:salamext:
First of all, you have to realise that prophets can make mistakes/errors, and they don't commit major sins at all.
The situation of the prophets is that if a prophet makes a mistake - Allaah Almighty corrects their mistake within their life (either through revelation, or by making the prophet realise the mistake) so the prophet can correct that error.
This means that Allaah Almighty doesn't leave that mistake alone, and the prophet realises that they have to correct it, and your example of when our beloved Prophet Muhammad (peace be upon him) turned away from the blind man is a good example, because just when the situation had happened, Allaah Almighty revealed the ayah/verse:
He frowned and turned away
Because there came to him the blind man (interrupting).
Surah Abasa [chapter 80 in the Qur'an verses 1 & 2]
That example shows that Allaah Almighty corrected the mistake through revelation, just when the situation happened. And it was not a sin;
(Of him you are neglectful and divert your attention to another.) meaning, `you are too busy.' Here Allah commands His Messenger to not single anyone out with the warning. Rather, he should equal warn the noble and the weak, the poor and the rich, the master and the slave, the men and the women, the young and the old. Then Allah will guide whomever He chooses to a path that is straight. He has the profound wisdom and the decisive proof.
It was only a command and a reminder, and it was an example to the believers that we should give da'wah (call to) islam to all sorts of people, no matter what status they may have etc.
You can read more about that from this link insha'Allaah:
http://www.tafsir.com/default.asp?sid=80&tid=57057
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You can read abit more about the story of Adam (alayhi Salaam) off the following link insha'Allaah, to get a better understanding insha'Allaah.
http://www.islamicboard.com/prophets...phet-adam.html
The main point is, that Allaah Almighty will correct the mistakes of the prophets in this life - so they leave this world without any sins, and with a perfect ending so the prophets can be an example for all of mankind.
Allaahu ta'aala a'lam. (Allaah Almighty knows best.)