One question that comes up a number of times in the Talmud is whether we take seriously the claim of a person who writes a conditional geṭ and argues that he did not mean to fulfill the condition, but that circumstances beyond his control kept him from doing so (ones be-giṭṭin).
An example of a conditional divorce is when a man writes a geṭ to his wife that says “this will be your bill of divorce if I do not return within 30 days” and at the end of the 30 days the husband is stranded on the wrong side of the river with no ferry to take him across. Even though he is shouting, “I have returned! I have returned!” we do not consider him to have come back and the divorce goes into effect.
Although this case seems to support the contention that ein ones be-giṭṭin – that we do not accept the husband’s claim – the Gemara in Massekhet Ketubot (2b–3a) explains that being stranded on the wrong side of the river with no available ferry to take him across was an ones that should have been anticipated and made part of the conditions of the divorce. Since it was not done that way, we do not consider it to be a true ones.
The ferry to which the Gemara refers here is called a ma’abra – a small boat or raft that took people across the river. Such ferries usually made several crossings every day, with a group of people each time. Generally speaking, it was not worthwhile for the owner of the ferry to cross the river with just one passenger, so people had to wait until the boat filled up before it would set sail. When the rivers were wide and deep – as was the case in Babylon – there was no other way to cross the river aside from these ferries, and if the boat was on the opposite bank of the river it may have even been possible that the boat’s captain would not realize that someone was waiting on the other side of the river for him. Thus, problems of crossing the river should have been taken into account by someone who made a condition to return by a certain time.