Sayyiduna al-Bara' bin Azib (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "On the day of sacrifice the very first thing is the prayer, and after it the sacrifice is made. Whoever adopts this way has attained the Sunnah. And whoever sacrifices before the prayer, it is only meat that he has presented to his family; it has nothing to do with the sacrificial rite." Sayyiduna Abu Burdah bin Niyar al-Ansari (may Allah be pleased with him) said: I have sacrificed before the prayer, but I have a jadha'ah which is better than a two-toothed animal. He (peace and blessings be upon him) said: "Very well, but it will not suffice for anyone after you."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19058