Sahih Bukhari Volume 7, Book 73, Hadith 5547

حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا غُنْدَرٌ، حَدَّثَنَا شُعْبَةُ، عَنْ زُبَيْدٍ الإِيَامِيِّ، عَنِ الشَّعْبِيِّ، عَنِ الْبَرَاءِ ـ رضى الله عنه ـ قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ إِنَّ أَوَّلَ مَا نَبْدَأُ بِهِ فِي يَوْمِنَا هَذَا أَنْ نُصَلِّيَ ثُمَّ نَرْجِعَ فَنَنْحَرَ، مَنْ فَعَلَهُ فَقَدْ أَصَابَ سُنَّتَنَا، وَمَنْ ذَبَحَ قَبْلُ فَإِنَّمَا هُوَ لَحْمٌ قَدَّمَهُ لأَهْلِهِ، لَيْسَ مِنَ النُّسُكِ فِي شَىْءٍ ‏"‏‏.‏ فَقَامَ أَبُو بُرْدَةَ بْنُ نِيَارٍ وَقَدْ ذَبَحَ فَقَالَ إِنَّ عِنْدِي جَذَعَةً‏.‏ فَقَالَ ‏"‏ اذْبَحْهَا وَلَنْ تَجْزِيَ عَنْ أَحَدٍ بَعْدَكَ ‏"‏‏.‏ قَالَ مُطَرِّفٌ عَنْ عَامِرٍ عَنِ الْبَرَاءِ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ مَنْ ذَبَحَ بَعْدَ الصَّلاَةِ تَمَّ نُسُكُهُ، وَأَصَابَ سُنَّةَ الْمُسْلِمِينَ ‏"

Narrated By Al-Bara : The Prophet said (on the day of Id-al-Adha), "The first thing we will do on this day of ours, is to offer the ('Id) prayer and then return to slaughter the sacrifice. Whoever does so, he acted according to our Sunna (tradition), and whoever slaughtered (the sacrifice) before the prayer, what he offered was just meat he presented to his family, and that will not be considered as Nusak (sacrifice)." (On hearing that) Abu Burda bin Niyar got up, for he had slaughtered the sacrifice before the prayer, and said, "I have got a six month old ram." The Prophet said, 'Slaughter it (as a sacrifice) but it will not be sufficient for any-one else (as a sacrifice after you). Al-Bara' added: The Prophet said, "Whoever slaughtered (the sacrifice) after the prayer, he slaughtered it at the right time and followed the tradition of the Muslims."