“When one of you is invited, he should respond. If he is fasting, let him pray (supplicate); and if he is not fasting, let him eat.”
Narrated by Muslim (no. 1431) from the ḥadīth of Abū Hurayrah (may Allah be pleased with him). In his wording (no. 1150): “Let him say: ‘I am fasting.’”
And in another narration by Muslim (no. 1429): “If one of you is invited to a wedding feast, he should respond,” from the ḥadīth of Ibn ʿUmar (may Allah be pleased with them both).
It was also narrated by Muslim (no. 1430) from the ḥadīth of Jābir (may Allah be pleased with him) with the wording: “If he wishes, let him eat; and if he wishes, let him refrain.”
Brief Explanation of the Hadith
Islam came with encouragement toward affection and mutual love, and one of the means to achieve this is responding to invitations, which is among the mutual rights of Muslims. As narrated from Abū Hurayrah (may Allah be pleased with him), the Prophet (may Allah’s peace and blessings be upon him) said: “When one of you is invited, he should respond.” That is, if he is invited to a wedding feast or any other permissible gathering, he should accept the invitation. “If he is fasting, let him pray,” meaning that he should attend and supplicate for the hosts, asking Allah to bless them and replace their provision, which is the meaning of “let him pray.” In another narration, it says: “Let him say: ‘I am fasting,’” meaning he should inform the hosts as a form of excuse, so that no ill thoughts are entertained regarding him. This applies when the fast is obligatory, such as making up a missed fast of Ramadān, or a fast of a vow or expiation; in such cases, it is incumbent upon him to complete it, and he is not permitted to break it. If the fast is voluntary, he has the option either to eat or to continue fasting. The preferred course is to eat if he sees that doing so will please the inviter, which is the meaning of: “And if he is not fasting, let him eat.”
The apparent meaning of the ḥadīth is that it is obligatory to respond to a banquet invitation unless a legitimate excuse exists—such as if the food is questionable, if the invitation is exclusively for the wealthy and excludes the poor, if the gathering is for an unlawful purpose, or if the assembly involves wrongdoing that one is unable to denounce, and the like of such excuses recognized by Islamic law. In such cases, responding to the invitation is not obligatory.