Parshes Lech Lecha

After Avraham got to the land of Cannan, the land was struck by a famine and Avraham - putting his wife in moral danger, went down to Mitzraim. How was it that Avraham left the land to which he was directed and did not trust Hashem the one who knows how to provide in hunger and desert? How did he seemingly expose the moral well-being of his wife to such a danger just to save himself? The Ramban writes; "Avraham comitted a grave sin in his behaviour towards his wife and even deserting the land to which he had been directed was already a sin". All the meforshim are bothered and try to explain this Ramban; How can- and for what purpose- does the Ramban write that Avraham sinned? R' S. R. Hirsch Zatza"l offers us an insight into the way the Torah looks at- and teaches us about- our forefathers and great men. (The following is a direct quote taken from the R' Isaac Levy - Judaica Press traslation.)
"This statement should not worry or mislead us. The Torah never presents our great men as being perfect and says of none "here you have the ideal, in this man the divine becomes human". Altogether it puts the life of no man before us as the pattern out of which we are to learn what is right and good, what are we to do, what to refrain from doing. Where the word of Hashem would set a pattern for us to imitate - it places no man born of dust - there Hashem says "look at me, imitate me, wander in my ways". We are never to say: This must be right for did not so-and-so do it! The Torah isn't "collection of examples of saints". It relates what occurred, not because it was exemplary, but because it did occur.
The Torah never hides from us the faults, errors and weaknesses of our great men. Just by that it gives the stamp of veracity to what it relates. But in truth, by the knowledge which is given us of their faults and weaknesses, our great men are in no wise made lesser but actually greater and more instructive. If they stood before us as the purest models of perfection we should attribute them to having a different nature, which has been denied to us. Were they without passion, without internal struggles, their virtues would seem to us as an outcome of some higher nature, hardly a merit and certainly no model that we could hope to emulate. Take for instance Moshe's humility. Did we not see that he could also fly into a passion, his meekness and modesty would seem to us to be his natural disposition, and lost to us as an example. Just his שמעו נא המורים gives his humility its true greatness, shows it to us as a result of a great work of self-control and self ennoblement which we all should copy- for we all could copy."