When working with nikhsei melug – which remain the property of the wife even as her husband derives benefit from it – there is a need to protect the interests of the wife in making sure that the property will not be destroyed, as well as the interests of the husband so that he will take care of the property, even though it does not belong to him.
Take, for example, the case of a man who is married to an underage girl who can reject the marriage when she reaches maturity (i.e. in a case where her mother or brother arranged the marriage in her father’s absence). Since he recognizes that their marriage can end at any time that his wife chooses, there is a real concern that the husband will be interested in deriving maximum profit from the property and pay no attention to the long-term value of the property. Therefore Rav Yaakov quotes Rav Ḥisda as teaching that in such a case, we treat the husband like anyone who gets permission to work someone else’s field, and he will be guaranteed the profits, even if the marriage is called off.
To illustrate this rule, the Gemara tells the story of a man who spent 600 zuz to travel to Bei Hozai where his wife had property. It turned out that the property was worth only 400 zuz, and that his expenses were larger than the property value itself. After some discussion of the matter, Rav Ami ruled that he deserves to get his expenses returned to him.
The long distance between Bei Hozai – which was an important center of agriculture and commerce – and the central Jewish community in Babylon, as well as the poor roads and infrequent caravans, could make the round trip take as long as a full year. Thus we can well understand how expensive such a trip might be.