If the father has a sum of forty thousand riyals owed to his son

The Shaykh : This is Umm Abdullah: A man has a son who owes him a sum of forty thousand riyals. He is forgiving him of it, even though the son has no job, so that the son can devote himself to his father, attend to his needs, and rely on him after Allah in everything. The son is the father of six daughters. I ask you, may Allah reward you with good, to clarify whether it is permissible for him to forgive him this amount or not, because he also has children?
We say: It is not permissible for him to forgive him this amount, because his son did that for the sake of Allah, that is, out of dutifulness to his father for the sake of Allah the Exalted, so he does not take a wage for it.