Is it obligatory to fast as an expiation for violating an oath by writing in a borrowed book, or is that considered a vain oath for which there is no expiation?

The questioner should have borrowed the book from a female colleague and avoided interacting with males except when necessary. The ruling on her oath varies depending on her intention:

- If she intended not to write anything that cannot be erased, then she must erase what she wrote with a pencil and return the book, and there is no expiation due upon her. - If she wrote something that cannot be erased: - If the oath was a laghw (i.e., uttered unintentionally), then there is no expiation due upon her. - If she intended the oath, then expiation for breaking an oath is due upon her: feeding ten needy persons, or clothing them, or freeing a slave. If she is unable to do so, then fasting for three days.