What is the reason behind the halacha that requires a man to refrain from being in a private quarters with a unrelated woman? Is this considered a sin? Is this just to ensure propriety or avoid the semblance of sin?
Answer:
Although the prohibition of yichud, meaning that one may not be in seclusion together with an unrelated woman, is a Torah prohibition (with regard to seclusion with a married woman; with regard to unmarried women, the prohibition is rabbinic), Rishonim explain that the reasoning behind the prohibition is to distance a person from sin. In the modern day, when scandals are common (and who knows how many cases there are that we don’t hear about), the logic behind the prohibition is clear. However, the actual being in seclusion with a woman is a sin, even if it does not lead to any further action.
Sources: See Rashi and Tosafos, Shabbos 13a, who state that yichud itself is a Torah prohibition — in spite of the fact that Tosafot (Sanhedrin 97) explain that the prohibition is out of concern that a person will come to sin. See also Beis Yosef (E.H. 22), who quotes from Rambam that the prohibition of yichud is not a Torah prohibition. However, according to all opinions, it is certainly an independent prohibition, whether Torah or rabbinic.
