Kiddushin 82A

הכל לשם שמים.

All such actions are permitted for the sake of Heaven. In other words, if one is acting out of familial affection, without any element of licentiousness, they are permitted.

מתני׳ לא ילמד אדם רווק סופרים. ולא תלמד אשה סופרים. רבי אלעזר אומר: אף מי שאין לו אשה לא ילמד סופרים. רבי יהודה אומר: לא ירעה רווק בהמה, ולא יישנו שני רווקין בטלית אחת, וחכמים מתירים.

Mishnah: A bachelor may not act as a teacher of children, nor may a woman act as a teacher of children. R' Elazar says: Even one who does not have a wife may not act as a teacher of children. R' Yehuda says: A bachelor may not herd cattle, nor may two bachelors sleep with one covering, lest they transgress the prohibition against homosexual sex, but the Rabbis permit it.

גמ׳ מאי טעמא? אילימא משום ינוקי, והתניא: אמרו לו לרבי יהודה: לא נחשדו ישראל על משכב זכור ולא על הבהמה! אלא: רווק ⁠– משום אמהתא דינוקי. אשה ⁠– משום אבהתא דינוקי.

Talmud: What is the reason that a bachelor may not teach children? If we say it is due to the children themselves, that it is suspected that he may engage in homosexual sex with them, but isn’t it taught in a baraita (Tosefta 5:10): They said to R' Yehuda: Jews are not suspected of engaging in homosexual sex nor of having sex with an animal. Rather, the reason is as follows: A bachelor may not be a teacher of children due to the mothers of the children, who come to the school from time to time, with whom he might sin. Similarly, a woman may not serve as a teacher to children because she may come to be secluded with the fathers of the children.

רבי אלעזר אומר אף מי שאין כו׳. איבעיא להו: מי שאין לו אשה כלל, או דלמא בשאינה שרויה אצלו? תא שמע: אף מי שיש לו ואינה שרויה אצלו לא ילמד סופרים.

The Mishnah teaches that R' Elazar says: Even one who does not have a wife may not act as a teacher of children. A dilemma was raised before the students in the study hall: Does R' Elazar mean one who does not have a wife at all, or perhaps he is referring even to one who has a wife, in a circumstance where she is not residing with him? Come and hear: Even one who has a wife but she is not residing with him may not act as a teacher of children. This statement is in accordance with the opinion of R' Elazar and indicates that his restriction applies even if the man is married.