Sahih Bukhari
Wedlock, Marriage (Nikaah)
Volume: 007 / Book Number: 062 / Hadith Number: 108
Narrated Nafi':
Abdullah bin 'Umar said, "Allah's Apostle said, 'Accept the marriage invitation if you are invited to it.' " Ibn 'Umar used to accept the invitation whether to a wedding banquet or to any other party, even when he was fasting.