Rabbi Joshua ben Hananiah did something in Rome that no Jewish sage was supposed to do. He entered the house of a Roman matron, locked the door behind him, spent time alone with her, bathed there, and left — without anyone questioning his integrity afterward (Gaster, Exempla No. 81).
That part is strange enough. The part that is stranger is that the sages, when they heard the story, did not suspect him.
Rabbi Joshua explained later. The matron was a secret ally of the Jews in matters of state. The locked door and the privacy were not for the sake of anything scandalous; they were for the sake of a meeting that could not be held in public. His life, and the safety of the community, depended on no one overhearing. The bathing that followed was not luxurious but ritual — he had come into contact with ceremonial impurity in the course of the errand and had to purify himself before returning to ordinary life.
The story has a deliberate shock at its center. The rabbis are teaching us that appearances can be arranged to look damning, and that a faithful man sometimes does things whose outer shape would condemn him if the inner purpose were not understood.
The lesson cuts two ways. We should never judge a righteous person by the keyhole. And we should guard our own actions so that, when they need to be explained, there is always an explanation worthy of a sage.