What is the Sharīʿah ruling on dealing with a father who borrows with interest (ribā) and refuses to stop, who mistreats his son when he tries to advise him, and who severs ties with him?

If the father leases land in exchange for a loan to its owner, this is forbidden usury (riba) and must be gently and wisely prohibited, as it is one of the gravest major sins. The son is not obligated to give money to his father if he himself needs it, but he must be kind to him and dutiful to him within his means. The father's anger or aversion will not harm him if he has not fallen short in his duty to him.