Is it permissible to borrow from one's father to help a friend with the travel expenses for studying, and is it considered a debt that must be repaid even if the father passes away?

It is permissible to borrow when there is a need and the ability to repay, and the proof of this is the action of the Prophet, peace and blessings be upon him. The money borrowed from a father depends on his intention; if he intended it as a loan, then it is a debt that must be repaid, otherwise not. If the father dies before the repayment, the loan must be returned to the estate to be distributed among the heirs. It is permissible for the heirs to waive the debt if they are adult and sane.