From Sahih Muslim (Hadith 5067):
Jundab al-Bajali reported:I saw Allah's Messenger (ﷺ) observing ('Id) prayer on the Day of Sacrifice (10th of Dhu'l-Hijja) and then delivering a sermon and he said: He who sacrificed the (animal) before offering ('Id) prayer, he should offer again in its stead, and he who did not sacrifice the animal should slaughter it by reciting the name of Allah
Reference: Muslim 5067