Translation
(9) The Chapters on Marriage
كتاب النكاح
(24) Chapter: The Walimah (wedding feast)
(24) باب الْوَلِيمَةِ
Sunan Ibn Majah 1908 
It was narrated that Anas bin Malik said:
“I never saw the Messenger of Allah give a wedding feast for any of his wives like the feast he gave for Zainab, for which he slaughtered a sheep.”
حَدَّثَنَا أَحْمَدُ بْنُ عَبْدَةَ، حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، عَنْ ثَابِتٍ الْبُنَانِيِّ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ مَا رَأَيْتُ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ أَوْلَمَ عَلَى شَىْءٍ مِنْ نِسَائِهِ مَا أَوْلَمَ عَلَى زَيْنَبَ فَإِنَّهُ ذَبَحَ شَاةً ‏.‏
Grade :  Sahih (Darussalam)
Reference : Sunan Ibn Majah 1908
In-book reference : Book 9, Hadith 64
English translation : Vol. 3, Book 9, Hadith 1908