Whoever slaughters his sacrifice before the 'Eid prayer should repeat it Sahih al-Bukhari 5562
Arabic hadith text
حَدَّثَنَا آدَمُ، حَدَّثَنَا شُعْبَةُ، حَدَّثَنَا الأَسْوَدُ بْنُ قَيْسٍ، سَمِعْتُ جُنْدَبَ بْنَ سُفْيَانَ الْبَجَلِيَّ، قَالَ شَهِدْتُ النَّبِيَّ صلى الله عليه وسلم يَوْمَ النَّحْرِ فَقَالَ "مَنْ ذَبَحَ قَبْلَ أَنْ يُصَلِّيَ فَلْيُعِدْ مَكَانَهَا أُخْرَى، وَمَنْ لَمْ يَذْبَحْ فَلْيَذْبَحْ "
Translation
Narrated Jundab bin Sufyan Al-Bajali
I witnessed the Prophet (ﷺ) on the Day of Nahr. He said, "Whoever slaughtered the sacrifice before offering the `Id prayer, should slaughter another sacrifice in its place; and whoever has not slaughtered their sacrifice yet, should slaughter now."