Jundub b. ‘Abdallah said

I was present at the festival on the day of sacrifice along with Allah's Messenger ﷺ. He had done no more than finish his prayer and give the salutation when he saw the flesh of sacrificial animals which had been sacrificed before he finished his prayer. So he said, “Anyone who has sacrificed before he prayed (or, we prayed) must sacrifice another in place of it." In a version he said: The Prophet (ﷺ) prayed on the day of sacrifice, then delivered a sermon, then sacrificed, and he said, “Anyone who has sacrificed before he prayed (or, we prayed) must sacrifice another in place of it, and if anyone has not sacrificed he should do so in Allah’s name." (Bukhari and Muslim.)