"Esther was not involved in a dubious or temporary love affair but actually became the queen, reaching the heights of ambition and achievement which a woman in those days could perhaps hope for.
Nevertheless, Esther felt that her task was more important, and that it was up to her to represent the Jewish people at this moment.
When Mordecai confronted her with the choice between her mission or her rank, her status, and–not least–her life, he was making things very difficult for her.
On the one hand, Esther had attained the highest possible position, that of queen, and she was likely to lose it at one stroke.
On the other hand, if she betrayed her mission, she would be a traitor to her values and beliefs for the rest of her life.
The sages have evaluated a role of this kind in connection with both Yael and Esther: 'Better a transgression for the sake of heaven than a good deed which is not.'
This saying, dangerous to those who abuse it, expresses an understanding of the spiritual dedication that goes beyond mere personal danger and involves also a degree of personal humiliation, a renunciation of self.
From the point of view of the Jewish woman, Esther's role was not honorable.
Had she married a fellow Jew and become a decent housewife in the capital or elsewhere, the feeling would have been that she was fulfilling a mitzvah (for the sake of heaven or otherwise) in a perfect, dutiful way.
The very fact that she was in the palace to begin with was, in a certain sense, the result of a chain of 'transgressions in the name of God.'
Midrashic and Talmudic literature expands this notion and penetrates deep into the problem of this total devotion."
–Rabbi Adin Steinsaltz
From Biblical Images, p. 220, by Rabbi Adin Steinsaltz