One Who Cannot Fulfill His Vow Due to Illness

Question:
I got married and made a vow to Allah that if He granted me a child, I would fast three days every month. I have now developed an illness in my stomach, and the doctor has prohibited me from fasting; so I left off fasting those three days and only fast Ramadan. What is the ruling on leaving off the fasting of those three days?

Answer:
The Prophet (peace and blessings be upon him) said: So the one who vowed to Allah that if He granted him a child, he would fast three days every month, or if Allah cured him of his illness, he would fast three days every month, or if Allah granted him such-and-such a job, he would fast three days every month; he must fast when his objective is achieved, when the condition is met; fasting becomes obligatory for him. And if he falls ill, he makes it up. If he falls ill and Allah cures him, he makes up the days just like Ramadan. If he falls ill, he fasts after that. So if a person falls ill in any of the months, he fasts the three days after his recovery. He has no excuse for leaving that off, except if he is struck by an illness from which there is no escape and whose cure is not expected; in that case, he is excused just like in Ramadan. He expiates by feeding one poor person for every day.
Q: For every day in every month?

Answer: Every month.

The student: For every month that passes?

Answer: A sa' and a half for every month.

The student: Does it repeat continuously with the months?

Answer: Yes, just like Ramadan.