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  

An uncle of mine called Abu Burda, slaughtered his sacrifice before the ʿId prayer. So Messenger of Allah ﷺ said to him, "Your (slaughtered) sheep was just mutton (not a sacrifice)." Abu Burda said, "O Allah's Apostle! I have got a domestic kid goat." The Prophet ﷺ said, "Slaughter it (as a sacrifice) but it will not be permissible for anybody other than you" The Prophet ﷺ added, "Whoever slaughtered his sacrifice before the (ʿId) prayer, he only slaughtered for himself, and whoever slaughtered it after the prayer, he offered his sacrifice properly and followed the tradition of the Muslims."  

لَهُ رَسُولُ اللَّهِ ﷺ شَاتُكَ شَاةُ لَحْمٍ فَقَالَ يَا رَسُولَ اللَّهِ إِنَّ عِنْدِي دَاجِنًا جَذَعَةً مِنَ الْمَعَزِ قَالَ اذْبَحْهَا وَلَنْ تَصْلُحَ لِغَيْرِكَ ثُمَّ قَالَ مَنْ ذَبَحَ قَبْلَ الصَّلاَةِ فَإِنَّمَا يَذْبَحُ لِنَفْسِهِ وَمَنْ ذَبَحَ بَعْدَ الصَّلاَةِ فَقَدْ تَمَّ نُسُكُهُ وَأَصَابَ سُنَّةَ الْمُسْلِمِينَ  

"مَن ضَحَّى قَبْلَ الصَّلاة، فَإنَّمَا ذَبَحَ لنَفْسه، وَمَنْ ذَبَحَ بَعْدَ الصَّلاةِ، فَقَدْ تَمَّ نُسُكُهُ وَأَصَابَ سُنَّةَ الْمُسْلمينَ".  

"مَنْ ذَبَحَ بَعْدَ الصَّلاةِ تَمَّ نُسُكُه وَأَصَابَ سُنَّةَ الْمُسْلِمِينَ".