Praise be to Allah.
If a person reaches a stage of senility and feeble-mindedness, loses his or her mental capacity and is no longer aware, the obligations of fasting and prayer are waived, and he does not have to offer expiation, because one of the conditions of being accountable is that one should be of sound mind.
The Prophet (peace and blessings of Allaah be upon him) said: “The Pen has been lifted from three: from the sleeping person until he wakes up, from the minor until he grows up, and from the insane person until he comes to his senses.” Narrated by Abu Dawood (4403), al-Tirmidhi (1423), al-Nasaa’i (3432), Ibn Majaah (2041). Abu Dawood said: It was narrated by Ibn Jurayj from al-Qaasim ibn Yazeed from ‘Ali (may Allaah be pleased with him) from the Prophet SAWS (peace and blessings of Allaah be upon him). He added “and the senile”.
This hadeeth was classed as saheeh by al-Albaani in Saheeh Abi Dawood.
It says in ‘Awn al-Ma’bood: Senility refers to when the mind becomes no longer sound because of old age. What is meant here is the old man has lost his mind because of old age. The elderly person may become confused and lose his power of discernment, which means that he is no longer qualified to be regarded as accountable, but he cannot be called insane. End quote.
Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said: Fasting is not obligatory unless certain conditions are met: (i) being of sound mind; (ii) being an adult; (iii) being a Muslim; (iv) being able to do it; (v) being resident (i.e., not travelling); (vi) being free of menses or nifaas (post-partum bleeding), in the case of women.
With regard to the first, being of sound mind – the opposite is loss of reason, whether it is due to insanity or senility, meaning old age, or an accident which causes a person to lose consciousness and feeling. Such a person does not have to do anything, because he is no longer of sound mind. Based on this, this elderly person who has reached the stage of senility does not have to fast or feed the poor, because he is not of sound mind. End quote from Liqa’ al-Baab al-Maftooh (4/220).
With regard to the past, if she was in this state, and was not aware and could not understand anything, then she does not have to fast or offer expiation.
If she was aware and could understand, but she did not fast because she was sick, then one of two scenarios must apply:
1.If at that time she was hoping to recover from her sickness, but the sickness continued, then she does not have to do anything, because what she had to do was make up the fasts when she recovered, but she did not recover.
2.If at that time there was no hope of recovery, then she should offer expiation for each day, which is feeding one poor person, half a saa’ of the local staple food. If she did not offer this expiation, then you must offer it now from her wealth.
We ask Allaah to heal her and make her well, and to guide and help you.
And Allaah knows best.