Sayyiduna Jundub bin Sufyan Bajali (may Allah be pleased with him) narrates: We were with the Prophet Muhammad (peace and blessings be upon him) during the time of sacrifice. Some people slaughtered their animals before the prayer. When the Prophet (peace and blessings be upon him) returned and observed that those people had already slaughtered their animals before the prayer, he said: Whoever slaughtered his animal before the prayer should slaughter another animal in its place, and whoever did not slaughter until we had performed the prayer, then he should now slaughter, taking the name of Allah.
Hadith Referenceصحیح ابن حبان / كتاب الأضحية / 5913
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «الإرواء» (4/ 367): ق.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرط الشيخين