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.