Sahih al-Bukhari 985
Sahih al-Bukhari · Book 13: The Two Festivals (Eids) · If the Imam is asked about something while he is delivering the Khutba
Narrated Jundab:
حَدَّثَنَا مُسْلِمٌ ، قَالَ حَدَّثَنَا شُعْبَةُ ، عَنِ الأَسْوَدِ ، عَنْ جُنْدَبٍ ، قَالَ صَلَّى النَّبِيُّ صلى الله عليه وسلم يَوْمَ النَّحْرِ ثُمَّ خَطَبَ، ثُمَّ ذَبَحَ فَقَالَ " مَنْ ذَبَحَ قَبْلَ أَنْ يُصَلِّيَ فَلْيَذْبَحْ أُخْرَى مَكَانَهَا، وَمَنْ لَمْ يَذْبَحْ فَلْيَذْبَحْ بِاسْمِ اللَّهِ " .
On the day of Nahr the Prophet (ﷺ) offered the prayer and delivered the Khutba and then slaughtered the sacrifice and said, "Anybody who slaughtered (his sacrifice) before the prayer should slaughter another animal in lieu of it, and the one who has not yet slaughtered should slaughter the sacrifice mentioning Allah's name on it."