Is it permissible for parents to say to their child, "Do not do such-and-such, and if you do, I will not forgive you, and we will settle the matter on the Day of Resurrection," concerning an act that is not forbidden by Sharia, and what is the child's recompense if he does it?

It is permissible for parents to threaten their son with not forgiving him and to frighten him with the Day of Judgment if the forbidden act does not exceed the bounds of their obligatory obedience, meaning that it does not involve disobedience to Allah, nor harm to the son, nor an invalid purpose for the parents. If the son disobeys them, while obedience is obligatory, he is sinful, and the sin increases as their harm increases.

Disrespecting parents is among the major sins, and its punishments are manifested in Allah's displeasure with the disobedient child, and the hastening of punishment for him in this world. It may also be a reason for his own children to disobey him, for "recompense is of the same kind as the deed." It is worth noting that on the Day of Judgment, the disobedient person is under Allah's will, and repentance erases what came before it.