Narrated Ibn 'Abbas:A woman came to the Prophet (ﷺ) and said (to him) that one month's fast was due from her mother who had died. May I fulfill them on her behalf? He asked: Suppose some debt was due from your mother, would you pay it ? She replied: Yes. He said: So the debt due to Allah is the one which most deserves to be paid

English translation · Sunan Abu Dawud