Sahih Muslim , Book 8, Hadith 3337 (USC-MSA) ⓘ
Ibn Umar (Allah be pleased with him) reported that Allah's Messenger said: When any one of you is invited to a feast, he should attend it.
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا دُعِيَ أَحَدُكُمْ إِلَى الْوَلِيمَةِ فَلْيَأْتِهَا " .
also referenced under: Book 16, Hadith 112 (In-Book) & Hadith 1429 (Reference)