פירוש על יבמות 15:2

בבאה מן הקציר – like a case that took place where the people of the city went to reap wheat and a snake bit one of them and he died, and she came and announced it to the Jewish court and they sent forth and found that it (i.e., the case that took place) was like her words. But the Sages did not permit [her to get remarried] but rather it was an illustration that the matter should be something nearby. But she is not believed regarding something taking place abroad.

Bet Hillel says: we heard [such a tradition] only in respect of a woman who came from the harvest and [whose husband died] in the same country, and in a case similar to the one that happened.
Bet Shammai said to them: [the law is] the same whether the woman came from the harvest or from olive picking, or from grape picking, or from one country to another--the Sages spoke of the harvest only [because the incident to which they referred] occurred then.
Bet Hillel changed their view to rule in accordance with Bet Shammai.
This mishnah is a continuation of yesterday’s mishnah. It contains a debate between Bet Hillel and Bet Shammai over when a woman is believed to say that her husband died.
Section one: Bet Hillel limits the instances in which a woman is believed to say that her husband died. The only time she is believed is when she returned from working together with him at harvest time, and they were not returning from abroad but from the same country. This is similar to “the case that was” mentioned at the end of this section. The case to which the mishnah refers to is explained in the talmud as being a case where ten men went to work in a field and one was bitten by a snake and died. When the woman returned and said that her husband was dead, the court believed her and declared that women are believed when they testify that their husband had died. According to Bet Hillel, they are only believed in such a case because in such a case the husband’s death is so easily verifiable that it can be assumed that the woman would not lie.
Section two: Bet Shammai responds to Bet Hillel that although the law that a woman is believed to say that her husband died was connected to a certain case, it is not limited to that case or those like it. Rather a woman is believed to say that her husband died no matter where she returns from.

אלא בהוה – the case that took place, such it was and the same law applies to other places.