The Messenger of Allah ﷺ said, "When one of you is invited to a wedding feast, let him attend it."In another wording, "When one of you is invited to a wedding banquet, let him respond."In yet another, "When one of you invites his brother, let him respond, whether it be a wedding or something similar."
ان رسول الله ﷺ قال: إذا دعي أحدكم إلى وليمة فليأتها. وفي لفظ: إذا دعي أحدكم إلى وليمة عرس فليجب. وفي آخر: إذا دعا أحدكم أخاه فليجب عرسا كان أو نحوه.
Malik narrated it in the Book of Marriage (49) from Nafi, from Abdullah bin Umar, as mentioned. Bukhari narrated it in the Book of Marriage (5173), and Muslim in the Book of Marriage (96:1429), both through the route of Malik, with the same wording. The other two wordings are found in Muslim, the first through the route of Ubaydullah, and the second through the route of Ayub, both from Nafi, with the same content.Invitations to a meal are of two kinds, an invitation to a wedding banquet, and an invitation not connected to a wedding. The majority of scholars hold that accepting an invitation to a wedding banquet is obligatory, because it expresses joy and happiness at the marriage of one's Muslim brother, unless there is a valid excuse. As for an invitation not connected to a wedding, accepting it is recommended.There are many valid excuses, some of which Nawawi mentioned in his commentary on Muslim (9/235), where he said, "Among them are that the food may be of doubtful origin, or that it may be reserved only for the wealthy, or that someone present would be harmed by one's attendance with him, or that sitting with him would not be fitting, or that one is invited out of fear of his harm or out of desire for his status, or in order to help him in something wrongful, and that there be nothing forbidden present, such as wine, entertainment, silk furnishings, unmounted images of animals, or vessels of gold or silver. All of these are valid excuses for declining the invitation." End of quote.