Is the remaining property of a Mukatab obligated to be returned if he incurred debt to make the final payment, and the remaining property covers the debt?

Primary text

If the Mukatab incurred debt to pay for his manumission, and what remains in his possession from charity is sufficient to cover that debt, he is not obligated to return it. This is because he requires that amount due to the manumission agreement, resembling the necessity for the funds used in paying the manumission.