What is the ruling regarding a man's oath that he will not take anything from his wife's inheritance from her father, and that she would be unlawful to him if she were to take anything from this inheritance? And is there expiation for this, or does his wife become forbidden to him?

The question includes two issues:

First: The husband swore an oath not to take anything from his wife’s inheritance from her father. If he breaks his oath, an expiation for breaking an oath becomes binding upon him, unless he had an intention or a reason that prompted the oath, and that reason has since ceased.

Second: The husband swore an oath to forbid his wife to himself if she took anything from her father’s inheritance. The ruling on this depends on his intention. If his intention is realized, then what he intended will occur. If he had no intention, or if there was a compelling reason for the oath that has since ceased, then he does not break his oath.

One must be cautious of using words of prohibition (tahreem) in resolving marital disputes. It is not permissible for a husband to prevent his wife from her inheritance. In matters of dispute, it is best to refer to specialized authorities, such as Sharia (definition) courts.