Is a freed slave (Mukatab) obligated to return funds given to his master before he became unable to pay his manumission installments?

Primary text

The Mukatab is never obligated to return the funds delivered to his master prior to his inability to complete the installments. This is because the Mukatab spent the funds for the purpose for which they were given, and the ownership of the master over those funds became firmly established. The master's ownership over them did not cease, similar to the situation if the Mukatab were manumitted entirely. This differs from property remaining in the Mukatab's possession because the master's ownership had not yet been firmly established over that property before this point; the dispute centers on the initial establishment of ownership.