Sahih Bukhari
Al-Adha Festival Sacrifice (Adaahi)
Volume: 007 / Book Number: 068 / Hadith Number: 469
Narrated Jundab bin Sufyan Al-Bajali:
I witnessed the Prophet on the Day of Nahr. He said, "Whoever slaughtered the sacrifice before offering the 'Id prayer, should slaughter another sacrifice in its place; and whoever has not slaughtered their sacrifice yet, should slaughter now."