Sahih Bukhari
Al-Adha Festival Sacrifice (Adaahi)
Volume: 007 / Book Number: 068 / Hadith Number: 454
Narrated Anas bin Malik:
The Prophet said, "Whoever slaughtered the sacrifice before the prayer, he just slaughtered it for himself, and whoever slaughtered it after the prayer, he slaughtered it at the right time and followed the tradition of the Muslims."