Reference: Fataawa Ramadhaan – Volume 1, Page 247, Fatwa No.195
Majmoo’ Fataawa Ibn Baaz – Volume 3, Page 234-235
Question: Concerning an elderly man, stricken with paralysis in half his body, and unable to fast; If he fasts, then his sickness worsens.
Response: If the medical specialists have determined your sickness is one from which there is no hope of getting better, then you are not required to fast; Instead, you must feed a poor and needy person for every day for the duration of Ramadhaan. The amount of food [you are required to offer] is half a saa’ of the food of that land – being dates, rice or other than that; And if you were to offer lunch or dinner – either would suffice.
If, however, the medical specialists have determined your sickness is one from which there is hope of returning to good health, then you are not required to feed a poor and needy person; Rather, you are required to make up the days of fasting you have missed when Allaah has cured you. This is based upon the statement of Allaah (Subhaanahu wa Ta’aala):
And I ask Allaah to bless you by curing you from every illness, and to render that which has afflicted you a purification and expiation for all [your] sins; And also to endow you with fine patience and contentment [of your reward from Allaah], indeed this is from the best of requests (supplications).