Must the son return the remainder of the money he stole from his father, after the father forgave him and then came back demanding the money he had not yet returned to him?

A father's forgiveness of his son regarding money is considered a release and a waiver of his right, and "what is waived does not return." This is because a release is a waiver of a right and not a transfer of ownership, like a gift (hibah) in which a father may revoke. Jurists have stipulated that a father cannot go back on a debt from which he has released his son, even if it is argued that a release is a transfer of ownership, because the debt ceases to exist after the release. Nevertheless, it is recommended that the son fulfill his father's request and return the invested money to him as an act of kindness to his father.