Can I borrow money to perform the Hajj if my father asks me for the expenses of his Hajj?

Bearing the expenses of your father's Hajj is among the best acts of devotion and an aid to obedience to Allah. If you are able to borrow money to cover his Hajj expenses, then do so. But if you are unable, or if it would cause you harm, then do not borrow, and apologize to your father in the best possible way.