Must the father pay a fine of one million Riyals on behalf of his eldest son who is in hardship, knowing that the father is well-off? And what is the right of the other sons and daughters to this money?

A father is not obliged to pay his son's debt or a fine on his behalf, especially if it resulted from something prohibited. However, if the son repents and regrets his actions, and the father is well-off, he should pay the fine on his behalf to spare him the harms of imprisonment. He is not obliged to give the other children the same amount because it is not a gift from which the son benefits.

However, if the father gives money to his son to trade in stocks for the son's benefit, and does not give to the others, he must be fair among them and give them the same, unless they agree to their brother being favored.