Study Guide Nedarim 27 A final difficulty is raised against Rava's explanation of the debate between Beit Hillel and Beit Shamai about the case where one cancels part of a vow. This difficulty is resolved as well. A braita is brought that is explained both according to Raba and according to Rava. The Mishna describes what is a vow of onasim, a vow that can't be fulfilled because of circumstances beyond one's control Rav Huna ruled in a case of one who was involved in a dispute with someone and when he went to search for more evidence in his favor, he handed in documents to the court that supported his claim and declared: If I don't come back in thirty days, these documents will be void. In the end, he didn't return due to circumstances beyond his control. Rav Huna ruled that the documents were void. Why is this case different from our Mishna - where circumstances beyond one's control are enough to dissolve the vow? Rava held that circumstances beyond one's control exempt one from responsibility. Why in a case of a get, though, is this not the case (when one says - this will be a get if I don't return and he died)? Or why is it different from a case when the man gives a get if he doesn't return within thirty days and on the thirtieth day he tries to get there but there is no ferry with which to cross the river? In both those cases, the get is valid. Returning to Rav Huna's ruling, the Gemara asks why is it not considered asmachta, a transaction where one does not fully consent to the arrangement as the outcome is unclear, which is considered not to be a valid acquisition. Is it different as the court is already in possession of the documents? Is that a relevant factor? Or is it different because he explicitly said that the documents should be canceled? The Gemara concludes that regarding asmachta, we rule that it is a valid acquisition as long as there was no oness, unexpected circumstance, and an act of acquisition was performed in an important court. There are certain circumstances where one can make a vow that one never intends to keep, such as, to a tax collector or to a murderer.