Ketubot 88 - Further arguments between the widow and the orphans
We learned earlier that when the widow comes to court, to collect her Ketubah, she must take an oath that her husband, while alive, did not already pay the Ketubah to her. Incidentally, such oaths apply to orphans as well.
For example, if the children of one family, after their father died, claim that the father of the other family (who also died) borrowed money from their father, and the children of the borrower say "Our father told us that he indeed borrowed, but repaid" - the children of the borrower must take an oath. This applied when their father says "I paid," for then the existence of the loan document does not prove anything.
However, if their father said, "I never borrowed," then it works against him. "I never borrowed" means automatically that he, of course, never repaid. Since the loan is uncontested and is documented, no oath helps, and the orphans need to pay the debt. Furthermore, this is only when the children are adults, but minors are more protected from the claims of others.
Art: The Children by Henri-Jules-Jean Geoffroy