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 1974

Salama b. al-Akwa' reported Allah's Messenger (way peace be upon him) having said:

He who sacrifices (animal) among you nothing should be left in his house (out of its flesh) on the morning of the third day. When it was the next year they (his Companions) said: Should we do this year as we did daring the previous year? Thereupon he said: Don't do that, for that was a year when the people were hard pressed (on account of poverty). so I wanted that the (flesh) might be distributed amongst them.
حَدَّثَنَا إِسْحَاقُ بْنُ مَنْصُورٍ، أَخْبَرَنَا أَبُو عَاصِمٍ، عَنْ يَزِيدَ بْنِ أَبِي عُبَيْدٍ، عَنْ سَلَمَةَ، بْنِ الأَكْوَعِ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ مَنْ ضَحَّى مِنْكُمْ فَلاَ يُصْبِحَنَّ فِي بَيْتِهِ بَعْدَ ثَالِثَةٍ شَيْئًا ‏"‏ ‏.‏ فَلَمَّا كَانَ فِي الْعَامِ الْمُقْبِلِ قَالُوا يَا رَسُولَ اللَّهِ نَفْعَلُ كَمَا فَعَلْنَا عَامَ أَوَّلَ فَقَالَ ‏"‏ لاَ إِنَّ ذَاكَ عَامٌ كَانَ النَّاسُ فِيهِ بِجَهْدٍ فَأَرَدْتُ أَنْ يَفْشُوَ فِيهِمْ ‏"‏ ‏.‏
Reference : Sahih Muslim 1974
In-book reference : Book 35, Hadith 46
USC-MSA web (English) reference : Book 22, Hadith 4862
  (deprecated numbering scheme)