Is it permissible to marry without the father's permission, and is it permissible for a woman to marry without her guardian (wali), with the presence of witnesses and a dowry, to avert fitna?

A young man must marry if he fears falling into haram (unlawful acts). The father's permission is not required in this case, and his obedience is not obligatory. It is advisable to conceal the marriage from the father if one despairs of his approval, while still maintaining dutifulness towards him. A man is not permitted to marry a woman except with the permission of her guardian, as a guardian is obligatory for marriage.