What is the ruling on obeying a father who insults the mother and children and uses violence against them, and is it obligatory to obey him in his command not to visit him except on the condition of marriage, knowing that the children believe the father does not believe in divine decree?

You must be patient with your father and treat him kindly. Righteousness towards parents is one of the greatest acts of obedience, while disobedience to them is a major sin. Allah Almighty has commanded kindness towards them and to lower the wing of humility to them, and He has forbidden saying "uff" to them or scolding them. Part of showing righteousness to him is offering him advice in a kind manner, especially regarding the preservation of prayer. The rights of parents remain, even with their ill-treatment, and one must accompany them with kindness, even if they strive to make their child associate partners with Allah. A father is not permitted to beat his child severely or to raise a weapon against him. However, light beating for discipline is permissible without excess. Obedience to the father is obligatory in what is good, and this includes his command to marry, as long as there is no disobedience to Allah or inability to bear expenses. The father's strictness in taking precautions does not mean he disbelieves in divine decree and destiny.