R' Eliezer also said: They can find grounds to annul a neder on the basis of an unexpected development; the Sages, however, prohibit it. How? [If] he said: “Konam, my having benefit from So-and-so,” and he became a scribe, or was shortly to marry off his son, and he said: “If I had known that he would become a scribe, or that he was about to marry off his son, I would not have made the neder!”; [or if one said:] “Konam, this house, with respect to my entering [it],” and it was made into a synagogue, [and] he said: “If I had known that it would be made into a synagogue, I would not have made the neder!” —- R' Eliezer permits it; the Sages, however, forbid it.

R' Meir says: There are things which are like unexpected developments, and are not like unexpected developments; the Sages, however, do not agree with him. How? [If one] said: “Konam, my marrying So-and-so, because her father is evil,” [and] they told him: “He died,” or that he had repented; “Konam, this house, with respect to my entering because an evil dog is in it” or “because a snake is in it,” [and] they told him: “The dog died,” or that the snake had been killed —- these are things which are like unexpected developments, but are not like unexpected developments. The Sages, however, do not agree with him.

R' Meir also said: They can find ground to annul his neder from what is written in the Torah, and they say to him: “If you had known that you transgress `You shall not take vengeance' (Lev. 19:18), or `You shall not bear a grudge' (ibid.), or `You shall not hate your brother in your heart' (ibid. v. 17), or `You shall love your fellow as yourself' (ibid. v. 18), [or] `That your brother may live with you' (ibid. 25:36) —- perhaps he will grow poor, and you will not be able to support him [would you have vowed?]” If he said: “Had I known that this was so, I would not have made the neder!” —- it is permitted.

They can find grounds to annul a man's neder by [reason of] his wife's kesubah. It happened once that a person made a neder prohibiting benefit from his wife, and her kesubah was four hundred dinars. He came before R' Akiva, who obligated him to pay her kesubah to her. He said to him: “Rabbi! Father left eight hundred dinars, my brother took four hundred, and I took four hundred. Is it not enough that she should take two hundred and I, two hundred?” R' Akiva said to him: “Even if you have to sell the hair on your head, you must pay her kesubah to her.” He said to him: “Had I known that this was so, I would not have made the neder.” Thereupon, R' Akiva permitted her.