The sick Person who is not strong enough to fast
Question :
There is a person who is ill with tuberculosis and it is difficult for him to fast during Ramadhan. Last Ramadhan he did not fast, so does he have to give food since it is known that he is not expected to recover from this illness?
Answer:
If this sick person is not strong enough to fast Ramadhan and he is not expected to recover from the illness, he is not obligated to fast. Instead, it is obligatory for him to feed a poor person for each day that he does not fast. He gives the person half a Sa' of wheat or dried dates or rice or something similar to that from the customary food of his people that they eat if he is able to do so. This is similar to the extremely old man and woman upon whom fasting is too difficult.
Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 3 Page 281