It was narrated that Ibn 'Abbas (رضي الله عنه) said: A man came to the Prophet (ﷺ) and said:

O Messenger of Allah, my mother has died and she owed a month's fast; should I make it up for her? He said: "If your mother owed a debt, would you pay it off for her?" He said: Yes. He said: "A debt owed to Allah is more deserving of being paid off.”