question #1 Sahih Muslim 1148d, Book 13, Hadith 202 : What is the ruling on fulfilling vows made by deceased relatives in Islam?

A woman came to the Messenger of Allah (ﷺ) and said: Messenger of Allah, my mother has died and there is due from her a fast of vow; should I fast on her behalf? Thereupon he said: You see that if your mother had died in debt, would it not have been paid on her behalf? She said: Yes. He (the Holy Prophet) said: Then observe fast on behalf of your mother.