Hadith: The Prophet (may Allah's peace and blessings be upon him) delivered a sermon after having offered the prayer on Eid al-Ad'ha. He said: Whoever prayed our prayer and slaughtered our sacrifice has properly observed the ritual. And whoever slaughtered (his sacrifice) before the (Eid) prayer has not observed the ritual - Encyclopedia of Translated Prophetic Hadiths

Hadith: The Prophet (may Allah's peace and blessings be upon him) delivered a sermon after having offered the prayer on Eid al-Ad'ha. He said: Whoever prayed our prayer and slaughtered our sacrifice has properly observed the ritual. And whoever slaughtered (his sacrifice) before the (Eid) prayer has not observed the ritual - Encyclopedia of Translated Prophetic Hadiths