Does a father have the right to reclaim a specific amount of money from his son, which he had lent to him,…

Does a father have the right to reclaim a specific amount of money from his son, which he had lent to him, after he had voluntarily waived the amount without coercion or undue pressure? The father had repeatedly waived the same amount in this manner, and to confirm this, a document was written and signed by both the father and the son, with some witnesses attesting to the father's waiver. After a period of time, the father then requested to cancel what he had pledged to waive, claiming that he had waived it out of shyness, although he acknowledged that the waiver was made without coercion or pressure from the son?