What is the ruling on a father refusing to return money that his son gave him for business purposes?

If the father is poor and the son is rich, it is obligatory for the son to spend on his father, and this spending cannot be considered a loan. However, if the father is rich or the son is poor, it is permissible for the son to lend money to his father, and the father must repay the debt when able, and he is not permitted to procrastinate. If he is in straitened circumstances, the son must grant him a delay. The son may demand repayment of the debt from his father if the latter is able to repay, but the father should not be imprisoned due to his son's debt; this is the view of the majority of scholars.