Sheikh Muhammad Al-Ansi ḥafidhahullāh responded:

"If your cooperation with your father involves repaying the money he borrowed—the principal amount from the bank—there is no issue with that; because it is originally a debt. However, do not assist him with the interest. For example, if he borrowed one hundred thousand euros or dollars, and they are charging an additional amount, such as two thousand dollars, you should help him pay back only the principal amount he borrowed. Do not assist him with the interest. This way, you avoid participating in sin, transgression, and the consumption of usury. The Prophet ﷺ cursed those who consume usury and those who facilitate it. Additionally, in this way, you are being kind and dutiful towards your father. Allah knows best."