كتاب الأضاحى
35  
The Book of Sacrifices
(1)
Chapter: The time for sacrifice
(1)
باب وَقْتِهَا ‏‏
Sahih Muslim 1960 b

Jundab b. Sufyan reported:

I was with Allah's Messenger (ﷺ) (on the occasion) of 'Id al-Adha. After he had completed the prayer with people, he found that the goats had been slaughtered, whereupon he said: He who slaughtered sacrificial animal before the prayer should slaughter a goat (again) in its stead and he who has not slaughtered he should slaughter it by reciting the name of Allah.
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو الأَحْوَصِ، سَلاَّمُ بْنُ سُلَيْمٍ عَنِ الأَسْوَدِ، بْنِ قَيْسٍ عَنْ جُنْدَبِ بْنِ سُفْيَانَ، قَالَ شَهِدْتُ الأَضْحَى مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَلَمَّا قَضَى صَلاَتَهُ بِالنَّاسِ نَظَرَ إِلَى غَنَمٍ قَدْ ذُبِحَتْ فَقَالَ ‏ "‏ مَنْ ذَبَحَ قَبْلَ الصَّلاَةِ فَلْيَذْبَحْ شَاةً مَكَانَهَا وَمَنْ لَمْ يَكُنْ ذَبَحَ فَلْيَذْبَحْ عَلَى اسْمِ اللَّهِ ‏"‏ ‏.‏
Reference : Sahih Muslim 1960b
In-book reference : Book 35, Hadith 2
USC-MSA web (English) reference : Book 22, Hadith 4819
  (deprecated numbering scheme)