The Messenger of Allah ﷺ said, "Accept this invitation when you are invited to it."The narrator said, Abdullah used to attend invitations, whether for a wedding or otherwise, even while he was fasting.
قال رسول الله ﷺ: أجيبوا هذه الدعوة إذا دعيتم لها قال: كان عبد الله يأتي الدعوة في العرس وغير العرس وهو صائم.
Bukhari narrated it in the Book of Marriage (5179), and Muslim in the Book of Marriage (14:1429:103), both through the route of Hajjaj bin Muhammad, from Ibn Jurayj, who said, Musa bin Uqba told me, from Nafi, who said, I heard Abdullah bin Umar, and he related it.As for what is narrated from Ibn Umar, that the Messenger of Allah ﷺ said, "Whoever is invited and does not respond has disobeyed Allah and His Messenger, and whoever enters without an invitation enters as a thief and leaves as a plunderer," this is daif. Abu Dawud (3741) and Bayhaqi (7/265) narrated it, both from the hadith of Darast bin Ziyad, who said, Aban bin Tariq told us, from Nafi, from Ibn Umar, and he related it.Regarding Darast bin Ziyad, Bukhari said of him, "His hadith does not stand." Ibn Hibban said, "He is extremely munkar in his hadith." As for Aban bin Tariq, Abu Zura said of him, "He is unknown." Ibn Adi mentioned this hadith and said, "He alone transmitted this hadith," and said, "This is the most munkar thing that has come from him."There is also a version on this subject from Ayesha, but it likewise does not sahih. Bayhaqi and others narrated it.