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 (ʿId) 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."  

قَالَ النَّبِيُّ ﷺ 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 ﷺ مَنْ ذَبَحَ بَعْدَ الصَّلاَةِ تَمَّ نُسُكُهُ وَأَصَابَ سُنَّةَ الْمُسْلِمِينَ  

The Prophet ﷺ said, "Whoever slaughtered the sacrifice before the prayer, he just slaughtered it for himself, and whoever slaughtered it after the prayer, he slaughtered it at the right time and followed the tradition of the Muslims."  

قَالَ النَّبِيُّ ﷺ مَنْ ذَبَحَ قَبْلَ الصَّلاَةِ فَإِنَّمَا ذَبَحَ لِنَفْسِهِ وَمَنْ ذَبَحَ بَعْدَ الصَّلاَةِ فَقَدْ تَمَّ نُسُكُهُ وَأَصَابَ سُنَّةَ الْمُسْلِمِينَ