Is it obligatory to write a will concerning the return of borrowed books to their owners if the borrower dies? And is it obligatory immediately, and must it be witnessed? And is it obligatory even if the borrower is not ill?

A will is not obligatory unless its absence leads to the loss of a rightful claim, such as when a person has a deposit or a loan without witnesses. If a will becomes obligatory and its owner writes it, there is no harm in it, and it is better to have witnesses to avoid the disagreement of the majority. Scholars have differed on the issue of immediacy, and it appears that if it becomes obligatory, then it is immediately obligatory, with a concession of up to three nights. As for the issue of illness, scholars mention it in defining the situation in which a general will becomes obligatory, and some have interpreted "the presence of death" in the verse of the will as referring to illness.