“I attended the ʿĪd al-Aḍḥā with the Messenger of Allah—may Allah’s peace and blessings be upon him. He did no more than lead the prayer and, upon completing it, gave the salām. Then he saw the meat of sacrificial animals that had been slaughtered before he had finished his prayer. He said: Whoever slaughtered his sacrifice before he prayed—or before we prayed—let him slaughter another in its place; and whoever has not yet slaughtered, let him slaughter in the Name of Allah.”

Narrated by al-Bukhārī (no. 5500) and Muslim (no. 1960), with the wording belonging to him, from the ḥadīth of Jundub ibn Sufyān (may Allah be pleased with him).

Brief Explanation of the Hadith

Since the uḍḥiyah is a great act of worship and a manifest rite of Islam, the Prophet (may Allah’s peace and blessings be upon him) clarified its rulings to his Companions in a comprehensive manner. Among these rulings is the time of slaughter. Jundub ibn Sufyān (may Allah be pleased with him) reported that after the Prophet (may Allah’s peace and blessings be upon him) completed the prayer, he saw that some people had slaughtered their sacrifices before the prayer had concluded. He then said: “Whoever slaughtered his sacrifice before he prayed—or before we prayed—let him slaughter another in its place.”
This contains a clear indication that slaughtering the uḍḥiyah before the ʿĪd prayer is not valid, for it is an act of worship restricted to a specific time. Thus, whoever did so is required to slaughter another in its place. An exception was made by some scholars in the case of one who acted out of ignorance of the ruling, holding that it would suffice for him. However, the majority maintained that it does not suffice, and they interpreted the ḥadīth of Abū Burdah (may Allah be pleased with him) as a special concession, based on his statement (may Allah’s peace and blessings be upon him): “And it will not suffice for anyone after you.”
His statement, “And whoever has not yet slaughtered, let him slaughter in the Name of Allah,” contains a command to pronounce the Name of Allah at the time of slaughter. A group of scholars held that this is a condition for the permissibility of the slaughtered animal. Others said that it is indeed a condition, but it is waived in cases of ignorance or forgetfulness. Still others held that it is a Sunnah; thus, the Muslim should be diligent in observing it at the time of slaughter.