Narrated Jundab:That he witnessed the Prophet (ﷺ) on the Day of Nahr. The Prophet (ﷺ) offered prayer and then delivered a sermon saying, "Whoever slaughtered his sacrifice before offering prayer, should slaughter another animal in place of the first; and whoever has not yet slaughtered any, should slaughter a sacrifice and mention Allah's Name while doing so

English translation · Sahih al-Bukhari