What is the required oath when someone claims to be the rightful heir of the creditor and the debtor denies this claim?

Primary text

If a person appears and claims to be the heir of the creditor, and the debtor denies this, the claimant must take an oath denying knowledge of the validity of their claim. This oath is required because it is an oath on the negation of another's act, thus it is on the negation of knowledge. If the debtor affirmed the claim, the debt would become due to the claimant. Since payment is obligatory upon affirmation, an oath is obligatory upon denial.