My father broke his fast in Ramadan in one of the years due to the hard work he was doing, and he did not make it up after that until he is now approximately ninety years old.

Question: My father broke his fast in Ramadan in one of the years due to the hard work he was doing, and he did not make it up after that until he is now approximately ninety years old. Although he is keen on obligatory and voluntary fasting, he did not make up that month. Is this voluntary fasting sufficient to make up for the missed days, or is it necessary to fast a full month with the intention of making it up? And given his current inability and advanced age, is it sufficient for him to pay expiation if he cannot fast, and what is the amount of the expiation?

Answer: Delaying the making up of the fast until this age is a great error, because the making up of the fast is a debt upon him. He must hasten to perform it and clear his conscience of it. As for leaving the making up of the fast for such a long period until he reached this age and became unable to fast, he has erred in that and been negligent, unless he was excused by the Shari'ah for this delay.
In any case, if he is able to make up the fast now, it is obligatory for him to make up this fasting. Along with making it up, he must feed a poor person for each day for the sake of the delay, by giving each poor person half a sa' (a dry measure of about 3 kg) of the food commonly eaten in the country. And if he is unable to fast, feeding is sufficient for him if his age has reached a point where he is unable to
fast, then feeding is sufficient for him to make up for the missed fast.because of His saying, the Exalted: [al-Baqarah: 184] .