Sunan Ibn Majah, Book 26, Hadith 3243 (In-Book) ⓘ
It was narrated that Muhammad bin Sirin said: “I asked Ibn ‘Umar about sacrifices and whether they are obligatory. He said: ‘The Messenger of Allah and the Muslims after him offered sacrifices, and this is the Sunnah.’”
حَدَّثَنَا هِشَامُ بْنُ عَمَّارٍ، حَدَّثَنَا إِسْمَاعِيلُ بْنُ عَيَّاشٍ، حَدَّثَنَا ابْنُ عَوْنٍ، عَنْ مُحَمَّدِ بْنِ سِيرِينَ، قَالَ سَأَلْتُ ابْنَ عُمَرَ عَنِ الضَّحَايَا، أَوَاجِبَةٌ هِيَ قَالَ ضَحَّى رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ وَالْمُسْلِمُونَ مِنْ بَعْدِهِ وَجَرَتْ بِهِ السُّنَّةُ .
also referenced under: Hadith 3124 (Reference) & Volume 4, Book 26, Hadith 3124 (DarusSalam)