It was narrated from Anas bin Malik that a man slaughtered on the Day of Sacrifice, (meaning) before the ‘Eid prayer, and the Prophet (ﷺ) ordered him to do it again.
Sunan Ibn Majah Book 26, Hadith 32
← Previous Hadith “Whoever among you sees the new crescent of Dhul-Hijjah and wants to offer a sacrifice, let him not take anything from his hair or nails.”

Sunan Ibn Majah Book 26, Hadith 31 Next Hadith → “I was present on Adha day with the Messenger of Allah (ﷺ), and some people slaughtered before the prayer. The Prophet (ﷺ) said: ‘Whoever among you has slaughtered before the prayer, let him repeat his sacrifice, and whoever has not, let him offer his sacrifice in the Name of Allah.’”

Sunan Ibn Majah Book 26, Hadith 33