Joseph, resisting the advances of his master Potiphar's wife, says that it was improper for him on two counts: firstly, because of the debt of gratitude that he owed Potiphar and, secondly, because it would be a terrible sin against God to commit adultery.
Rav Mordechai Gifter (1915-2001) raises an interesting question. Why, when repelling Potiphar wife's advances, did he not state why it was wrong and inappropriate for her, rather than him, to commit such an act? Rashi quotes a talmudic statement that even before the Torah was given, non-Jews were commanded against immorality.
Rav Gifter suggests that Joseph, sensing the severity of the test, felt that he was partially responsible for the situation owing to some shortcoming in his own personality. He believed that had he maintained the high level of sanctity befitting Jacob's favoured son, Potiphar's wife would never have imagined that she could sway the mind of such a righteous man, and so she would never have tried.
Joseph shows his greatness in openly admitting that he was not merely a victim of circumstance but that it was a gradual and subtle lowering of his own guard that led to the encounter with Potiphar's wife.
How often do we excuse much of our immoral behaviour, claiming to ourselves that we are just "victims of circumstance", who have little or no choice? Like Joseph, we should reflect on our past conduct and realise that our situation stems from a failure to erect the appropriate boundaries and pre-empt it arising in the first place.