R’ Meir says: Any condition which is not like the condition of the children of Gad and the children of Reuven is not a condition, as it says (Num. 32:29): And Moses said to them: If the children of Gad and the children of Reuven will cross ..., and it is written (ibid. v. 30): But if they will not cross zealously ... R’ Chanina ben Gamliel says: It was necessary for the matter to be stated, because otherwise, it is implicit that even in the Land of Canaan they shall not inherit.

[If] one betrothed a woman and said: “I thought that she is the daughter of a Kohen, and lo, she is the daughter of a Levi”; [or] “the daughter of a Levi, and lo, she is the daughter of a Kohen”; “a poor woman, and lo, she is a rich woman”; [or] “a rich woman, and lo, she is a poor woman” —- she is betrothed, because she did not deceive him.  [If] one says to a woman: “You are betrothed to me after I will be converted,” or “after you will be converted”; “after I become freed,” or “after you become freed”; “after your husband shall die,” or “after your sister shall die”; “after your yavam shall give you chalitzah” —- she is not betrothed.  Likewise, [if] one says to another: “If your wife bears a female, she is betrothed to me,” she is not betrothed. If the other’s wife was pregnant and her fetus was discernible, his words are effective; and if she bore a female, she is betrothed.