Answered by Ustadha Shaista Maqbool
i was fasting the sunnah fast a few mondays ago when i was invited for a meal. i broke the nafl fast in order to eat as i heard that a guest must abandon break the fast if invited for a meal. do i have to make-up now?
In the Name of Allah, Most Merciful, Most Kind.
If one starts a voluntary (nafl) fast and breaks it, he must make it up. There is no kaffarah (an atonement specified by the Law) for this. [Maraqi al-Falah]
“One who starts a voluntary fast may not break his fast without an excuse. Hosting a guest is an excuse for [both] the guest and the host if the guest or host is one who is not contented by the mere presence of the other and would be troubled by his not breaking his fast, otherwise [being a host/guest] is not [an excuse].” (Al-Durr
From the latter it becomes clear that one who is fasting a voluntary fast may break the fast if his host/guest is displeased with him not eating; If the latter is not the case, i.e. if his host/guest does not mind that he fasts, he may not break the fast.
The other conditions (of breaking a voluntary fast) are:
1) That it be before zawal time – i.e. the time before the sun reaches its zenith (which occurs slightly before Zhuhr time). He may not break his fast after this time.
2) That the person who is fasting is certain he will make up the fast if he breaks it, such that if he is not sure he will be able to keep another fast in place of it, he may not break his fast, even if his host/guest is displeased with him not eating. (From Hashiyah Ibn ‘Abideen)