Ketubot, Chapter Seven, Mishnah Four
This mishnah deals with a husband who attempts to prohibit his wife from seeing her father.
If a man forbade his wife by vow that she may not go to her fathers house:
–When the father lives with her in the same town, the husband may retain [her as his wife, if the prohibition was for] one month; but if for two months he must divorce her and give her the ketubah.
–When the father lives in another town, the husband may retain [her as his wife, if the prohibition was for] one festival, but if for three festivals, he must divorce her and give her the ketubah.
In the scenario in this mishnah, a husband makes a vow that prohibits his wife from visiting her father. You can imagine that this situation arose out of some tension between the two. The mishnah rules that if the father is in the same town, he can prohibit her for only one month. More than that, and he has to divorce her and give her the ketubah. Since they live in the same town, more than a month without seeing each other would be too long of an absence for her or perhaps her father to bear.
If the father lives in another town, the daughter assumedly sees him less frequently, and therefore the husbands prohibition is allowed to stand slightly longer. If he prohibits her for one festival (until the next festival), he may retain her as a wife. According to the Talmud, in order to understand this section of the mishnah we must add into the mishnah that if he prohibits her for two festivals (until two festivals have past), he must divorce her and give her the ketubah. If the husband was a priest, he may retain her if the prohibition was for two festivals, but must divorce her if for three. The Talmud adds this extra clause into the mishnah, for otherwise it doesnt deal with a prohibition of two festivals.