Is it permissible to fast on behalf of a deceased person?

Question: Is it permissible to fast on behalf of a deceased person if he did not fast during his lifetime in Ramadan? Even though he paid the expiation before his death.

Answer: It is prescribed for his relatives to fast on his behalf if he was a Muslim who prayed; based on the saying of the Prophet (peace and blessings be upon him): , which is agreed upon as authentic, unless he left off fasting due to his inability to do so because of old age or an illness that is not expected to end, in which case he owes no fasting. The feeding of the poor that he provided during his life is sufficient, if he provided it for all the days he missed.
As for if he did not pray, then the fasting he owed is not made up on his behalf; because one who intentionally leaves off prayer commits disbelief, major shirk, according to the most correct of the scholars' opinions; based on the saying of the Prophet (peace and blessings be upon him): , narrated by Imam Ahmad, Abu Dawud, al-Tirmidhi, al-Nasa'i, and Ibn Majah with a sound chain from Buraydah ibn al-Husayb (may Allah be pleased with him), and based on his saying (peace and blessings be upon him): , narrated by Imam Ahmad and al-Tirmidhi with a sound chain from Mu'adh ibn Jabal (may Allah be pleased with him), and based on his saying (peace and blessings be upon him): , narrated by Imam Muslim in his Sahih from Jabir ibn Abdullah (may Allah be pleased with them both).
The hadiths in this chapter are numerous, and we ask Allah for all Muslims to be guided to what pleases Him, and to be helped in performing what Allah has made obligatory upon them, such as prayer and others, in the manner that pleases Him, the Exalted. Indeed, He is All-Hearing, Near.