Question: I observe Sawm for three days every month. One month, I felt ill. Therefore, I could not observe Sawm (Fast). Do I have to make up or expiate for them?
Answer: There is no making up for the missed days of supererogatory Sawm even if a person missed them willingly. But it is better for the Muslim to continue doing good deeds according to the Saying of the Prophet (peace be upon him): The deed liked most by Allaah is one to which the doer adheres constantly even if it is small. So you do not have to make up or expiate for your missed supererogatory Sawm… read more here.