كتاب الأضاحى
35  
The Book of Sacrifices
(5)
Chapter: The prohibition of eating sacrificial meat for more than three days, which applied at the beginning of Islam but was then abrogated, and now it is permissible to eat it as long as one wants.
(5)
باب بَيَانِ مَا كَانَ مِنَ النَّهْىِ عَنْ أَكْلِ لُحُومِ الأَضَاحِيِّ بَعْدَ ثَلاَثٍ فِي أَوَّلِ الإِسْلاَمِ وَبَيَانِ نَسْخِهِ وَإِبَاحَتِهِ إِلَى مَتَى شَاءَ
Sahih Muslim 1970 a

Ibn 'Umar reported Allah's Apostle (ﷺ) having said:

None of you should eat the flesh of his sacrificial animal beyond three days.
وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، ح وَحَدَّثَنِي مُحَمَّدُ بْنُ رُمْحٍ، أَخْبَرَنَا اللَّيْثُ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم أَنَّهُ قَالَ ‏ "‏ لاَ يَأْكُلْ أَحَدٌ مِنْ لَحْمِ أُضْحِيَّتِهِ فَوْقَ ثَلاَثَةِ أَيَّامٍ ‏"‏ ‏.‏
Reference : Sahih Muslim 1970a
In-book reference : Book 35, Hadith 37
USC-MSA web (English) reference : Book 22, Hadith 4853
  (deprecated numbering scheme)