The Book of Marriage
وَحَدَّثَنِي مُحَمَّدُ بْنُ رَافِعٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنْ أَيُّوبَ، عَنْ نَافِعٍ، أَنَّ ابْنَ عُمَرَ، كَانَ يَقُولُ عَنِ النَّبِيِّ صلى الله عليه وسلم " إِذَا دَعَا أَحَدُكُمْ أَخَاهُ فَلْيُجِبْ عُرْسًا كَانَ أَوْ نَحْوَهُ " .Ibn Umar (Allah be pleased with them) reported Allah's Apostle (ﷺ) as saying:When any one of you invites his brother, he (the latter) should accept his wedding feast, or any other like it
From Sahih Muslim, whose reports the scholars accept as authentic.