Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) said: "When you are invited to a wedding feast (walimah), accept it." Khalid said: Ubaydullah applied it to the wedding (feast).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصداق / 14519