When Yosef was faced with the test of not succumbing to Eishes Potifar, he was aided by a visage of his father which appeared to him -- "dmus d'yukno shel aviv nirah lo." Why do Chazal use the passive voice, "nirah lo," instead of the active voice, i.e. "Ra'ah Yosef dmus d'yukno...?"
My wife suggested that Chazal use the passive voice to highlight the fact that Yosef was rescued through no merit or action of his own. It was only through isarusa d'leila, only by virtue of Divine intervention, that Yosef was spared.
In the footnotes to the sefer Shemu'os Rei'Ya"h (essays on Sefer Braishis based on torah said by Rav Kook) there is another suggestion quoted from an unnamed talmid chacham. Yosef was a carbon copy of Ya'akov in many aspects of his life (as Rashi notes at the beginning of VaYeishev), with one glaring exception. While Ya'akov was "yoshev ohalim," removed from the world and cloistered in the ivory tower of the beis medrash, Yosef felt he could maintain his tzidkus and also blend into society. These were two different philosophies of life. When Yosef was faced with the test of dealing with Eishes Potifar, he finally acknowledged, "nirah lo," as in the sense of being modeh to another point of view, that his father's approach had the advantage over his own.