Is a sick person who is unable to fast required to do so if a doctor orders against it, and is expiation due from them?

If a trustworthy Muslim doctor decides that fasting is harmful to a patient, then the patient should break their fast because they are ill. If the doctor determines that the illness is incurable, then there is no make-up fasting (qadaa') required for the patient. Instead, they should feed one poor person for each day, based on the Almighty's saying: "And upon those who are able to fast [but with hardship] - a ransom [as substitute] is feeding a poor person." Ibn Abbas clarified that this verse is a concession for the elderly man and the elderly woman who are unable to fast. The estimated amount for feeding is one mudd of food (approximately 750 grams) for each day. It is permissible to feed thirty poor people at once, or one poor person over thirty days.