Sahih Muslim Book 8, Hadith Number 3344.

Chapter: When one is invited to a wedding feast, one should accept it.

Nafil reported: I heard Abdullah b. Umar (Allah be pleased with them) narrating that Allah’s Messenger (May peace be upon him) said: Accept the feast when you are invited to it. And Abdullah (b. Umar) used to come to the feast, whether it was a wedding feast or other than that, and he would come there even in the state of fasting.