The ruling on prayer and fasting for one whose mind is impaired due to old age

Question:
In the name of Allah, the Most Gracious, the Most Merciful. The questioner says: Honorable Shaykh, my mother is very old and does not pray like she used to; rather, she loses track in her prayer. She fasts some days and completes the day, or perhaps she does not complete it. He asks: Does she have a sin upon her? And do we fast that day on her behalf, or do we pay the expiation for her?

Answer:
If a person is afflicted in his mind by old age, or by senility, or by dementia, or by a condition that has taken his mind, such that he does not perceive what he is doing and does not know about Ramadan or anything else, then he owes nothing. He is not accountable, because accountability follows the mind. As long as the mind is present, the Muslim must perform the acts of obedience and the obligatory duties according to his ability.
As for the one who has no mind and does not know, there is nothing required of him. And the sleeping person until he wakes up, and the insane person until he regains his senses. This is like the insane person who has no mind.
As for the one who has a mind but cannot fast—his mind is present and his perception is present, but he cannot fast—then he feeds people on his behalf. This applies to the old man and the chronically ill person; they feed people as a ransom, and this suffices for them in place of fasting.