The ruling on making up fasts on behalf of a mother who passed away without fasting

Question:
May Allah reward you and bless you. Another questioner from the Umm 'Abd al-Rahman program sent this question, saying: Shaykh, a woman in the past did not fast until she reached the age of twenty-five. After that, she became steadfast in obedience to Allah and maintained fasting, prayer, charity, and the night prayer, but she informed her daughter that she had not fasted in those years, and then she died. She says: My mother informed me of the fact that she had not fasted until she reached twenty-five. She asks: Should I fast on her behalf, or should I pay an expiation for the missed fasts of those years?

Answer:
If she did not pray during that period, having abandoned prayer along with fasting, then she is not upon Islam, because the one who does not pray is not a Muslim. Even if she fasted, the prohibition of fasting does not apply to the one who does not pray; rather, the one who does not pray does not invalidate fasting or anything else. But if she repented to Allah and maintained fasting and prayer, then Allah forgives us, and it is not obligatory for us to make up the fasts of one who has passed away. Or if she abandoned [prayer].
As for if she was steadfast in prayer, but she abandoned fasting out of negligence or ignorance, then it is obligatory for her to make up the fasts. But since she died, it is not obligatory for her to make them up for herself. If any of her relatives wishes to make up the fasts on her behalf, that is a great good and a reward for the one who does it.