If one breaks a voluntary fast, is it obligatory to make it up?

Question:
May Allah reward you, Honorable Shaykh. This questioner asks: Is it obligatory for a person to make up a voluntary fast if he breaks it due to illness or intercourse, or is there no obligation to make it up?

Answer:
The obligation to make up a fast applies only to what is obligatory. The compiler (may Allah have mercy on him) states that if one makes it up, that is better, merely as a recommendation, and there is no obligation to make up a fast except in the case of an obligatory fast.