Vowing to fast for three days every month if his third son was born naturally

Q: I am married with children. My second child was born by cesarean at hospital. Following his birth, I made a vow to Allah (Exalted be He) that if the third child was born normally, I would fast three days of every lunar month. It was Allah's will that I gave birth to a third child who was born normally. I continued to fast three days of every lunar month until I had my fourth child who was born by cesarean. As I was not sure regarding the fatwa of some scholars, I thought of sending this question to Your Eminence hoping that you will tell me whether I have to do Kaffarah or continue fulfilling my vow despite my inability.

A: You have to keep fasting three days of every month in fulfillment of the vow you made. You are only allowed to stop fasting if you are unable to fast the month of Ramadan, in which case you are required to do Kaffarah (expiation) for failing to fulfill the vow. This is based on the Hadith of the Prophet (peace be upon him) in which he said: "Whoever vows to obey Allah, should obey Him..." May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.