Yahya related to me from Malik from Nafi from Abdullah ibn Umarthat the Messenger of Allah, may Allah bless him and grant him peace,said, "When you are invited to a wedding feast, you must go to it." (AR)
USC-MSA web (English) reference: Book 28, Hadith 49 (AR)
Arabic reference (AR): Book 28, Hadith 1144 (AR)