Is it permissible for me to fast on behalf of my father who is unable to fast or feed the poor?

If the father is permanently unable to fast, he must feed a poor person for each day, according to the Almighty’s saying: "And upon those who are able to fast [but with difficulty], a ransom [as substitute] of feeding a poor person." And if he is unable to feed, then nothing is incumbent upon him. As for the son fasting on behalf of his father, it is not legislated, for every soul is pledged for what it has earned, and the evidence only indicates the legality of fasting on behalf of the deceased.