He was not able to pray before he died; can prayers be offered on his behalf?
Question

                What is the ruling on who died due to a grave illness and could not pray for one month and half then he died. Is it permissible for someone of his family to pray on behalf of him? If not then is there any expiation or not?.
Praise be to Allah.
    Firstly: 

    Prayer is the greatest pillar of Islam after the 
    Shahaadatayn, and it is not waived for anyone so long as he is of sound 
    mind. Whoever can pray standing must do that, otherwise he should pray 
    sitting or on his side, or by making gestures, according to what he is able 
    to do, and Allaah does not burden any soul beyond its scope. That is because 
    the Prophet  (peace and blessings of Allaah be upon him) said: “Pray 
    standing, and if you cannot, then sitting, and if you cannot, then on your 
    side.” Narrated by al-Bukhaari (1117). 

    The one who prays sitting should lean forward for bowing and 
    prostrating, making the prostration deeper than the bowing. 

    If he is unable to move his head, then should he gesture with 
    his eyes, or is prayer waived for him, or are the movements waived only and 
    not the words? The correct view is the third option. 

    Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said: 
    The most correct of these three views is that only the movements are waived, 
    because that is what he is unable to do. As for the words, they are not 
    waived in his case, because he is able to say them, and Allaah says 
    (interpretation of the meaning): 

    “So keep your duty to Allaah and fear Him as much as you 
    can”

    [al-Taghaabun 64:16]

    So we say: Say takbeer, recite Qur’aan, form the intention to 
    bow, say takbeer and the tasbeeh of bowing, then form the intention to stand 
    up, and say, Sami’a Allaahu liman hamidah Rabbana wa laka al-hamd 
    (Allaah hears those who praise Him, our Lord to You be praise), and so on. 
    Then form the intention to prostrate and say takbeer and the tasbeeh of 
    prostration, because this is what is dictated by the shar’i principle, 
    “So keep your duty to Allaah and fear Him as much as you can” [al-Taghaabun 
    64:16]. If a person is unable to say the words or do the movements, such 
    as if a man is paralyzed and cannot speak, what should he do? The answer is 
    that both the words and the movements are waived in his case, but the 
    intention remains, so he should form the intention that he is praying, and 
    form the intention to recite, and form the intention to bow, prostrate, 
    stand and sit. This is the correct view, because the prayer is words and 
    movements accompanied by the intention, so if the words and movements are 
    waived because of one’s inability to do them, there remains the intention. 
    And if we were to say to this sick person: You do not have to pray, that 
    might cause him to forget Allaah, because if a day and a night pass without 
    his praying, he may forget Allaah. So if we make him feel that he has to 
    pray even if it is only by intention, that is better than saying that he 
    does not have to pray. End quote from al-Sharh al-Mumti’ (4/469). 

    Based on that, if the person asked about reached a stage 
    where he could not pray in any of the ways mentioned above, then he is 
    excused and there is no sin on him. 

    Whether he was excused or not, if he failed to offer any of 
    the obligatory prayers, no one should pray on his behalf. This is the view 
    of the four imams (Abu Haneefah, Maalik, al-Shaafa’i and Ahmad – may Allaah 
    have mercy on them). 

    See: al-Mawsoo’ah al-Fiqhiyyah (2/334). 

    The scholars of the Standing Committee for Issuing fatwas 
    were asked: My mother died after suffering greatly from sickness, may Allaah 
    have mercy on her. She did not pray for ten days, during which she was 
    unconscious at some times and awake at others, but she did not pray during 
    these days. Should I pray on her behalf, or what should I do for her? Is it 
    permissible to send blessings on the soul of the deceased? 

    They replied: It is not permissible to offer prayers on 
    behalf of the deceased, whether she failed to offer them because of an 
    excuse or otherwise, or to pray with the intention that the reward for the 
    prayer should go to the deceased, because that is not prescribed in 
    sharee’ah. The Prophet  (peace and blessings of Allaah be upon him) 
    said: “Whoever does an action that is not part of this matter of ours will 
    have it rejected.” Narrated by Muslim in his Saheeh. End quote from
    Fataawa al-Lajnah al-Daa’imah (9/65). 

    It also says (25/257): If your father lost consciousness when 
    he became sick and was not aware of anything, then prayer was waived for 
    him, and he is not accountable when in this state, because accountability 
    for prayer is connected to reason and he no longer has it. But if he did not 
    lose consciousness or his reason, but he neglected prayer because he was 
    unaware that people in his position have to pray according to what they are 
    able to do, then we hope that Allaah will forgive him and excuse him for his 
    ignorance of that and for having no one who could explain the shar’i ruling 
    to him before he died – may Allaah have mercy on him and forgive him. 
    Whatever the case, it is not permissible for you to offer any prayers on 
    behalf of your father, because no one can pray on behalf of anyone else. The 
    basic principle is that prayer cannot be delegated. As for your doing Hajj 
    and ‘umrah on behalf of your father, that is a way of honouring him, and if 
    you give charity on his behalf from time to time, and pray for him and ask 
    for forgiveness for him and uphold ties with his relatives and friends and 
    treat them kindly, these are ways of honouring your father after his death, 
    and you will be rewarded greatly in sha Allaah for what you do. End quote. 

    To sum up: prayers cannot be offered on behalf of this 
    deceased, and there is no expiation for the prayers that he missed, but you 
    should pray for him (du’aa’) and give charity on his behalf. 

    And Allaah knows best.