Is a father's hitting his son for not praying with him, knowing that the son prays with his siblings before the prayer time ends, considered an injustice from the father or a mistake from the son?

You must obey your father and pray with him in the mosque if he commands you to do so, because this is a way of showing him piety and seeking his pleasure, avoiding the disagreement of those who consider congregational prayer in the mosque obligatory, and attaining complete reward. It is permissible for a father to discipline his child for disobeying his command, even if the disagreement is over an matter that is not a sin; rather, it is even more appropriate if the matter is disputed between being recommended and obligatory. For obedience to parents is obligatory even in doubtful matters.