Sahih al-Bukhari 5545
Narrated Al-Bara:
The Prophet (ﷺ) said (on the day of Idal-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 (ﷺ) 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 (ﷺ) said, "Whoever 
slaughtered (the sacrifice) after the prayer, he slaughtered it at the right time and followed the tradition 
of the Muslims."
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 ‏"‏‏.‏