He related this to us beside a column in the mosque and said, "Had I been there, I would have shown you the exact spot."He said, the Messenger of Allah ﷺ addressed us and said, "The first thing we begin with on this day of ours is that we pray, then we return and offer the sacrifice. Whoever does this has followed our practice, and whoever slaughtered before that, it is merely meat he has presented to his family and has nothing to do with the rite."My maternal uncle, Abu Burda bin Niyar, had slaughtered, and he said, "Messenger of Allah, I have slaughtered, but I have a young goat that is better than a mature one."He said, "Sacrifice it in place of the other, but it will not be sufficient or fulfill the duty for anyone after you."
حدثنا عفان حدثنا شعبة قال زبيد أخبرني منصور وداود وابن عون ومجالد عن الشعبي وهذا حديث زبيد قال سمعت الشعبي يحدث
وحدثنا عند سارية في المسجد قال ولو كنت ثم لأخبرتكم بموضعها قال خطبنا رسول الله ﷺ فقال إن أول ما نبدأ به في يومنا هذا أن نصلي ثم نرجع فننحر فمن فعل ذلك فقد أصاب سنتنا ومن ذبح قبل ذلك فإنما هو لحم قدمه لأهله ليس من النسك في شيء قال وذبح خالي أبو بردة بن نيار قال يا رسول الله ذبحت وعندي جذعة خير من مسنة قال اجعلها مكانها ولم تجزئ أو توف عن أحد بعدك
Its isnad is sahih, as its narrators through these routes are trustworthy authorities. Mujalid here is corroborated, so it may be accepted. The hadith has already appeared at 12110 and 12059 with similar wording.