Sayyiduna Jundub bin Sufyan (may Allah be pleased with him) says: I was with the Messenger of Allah (peace and blessings be upon him) on the day of sacrifice when a man said: "People have made their sacrifices before the prayer." He (peace and blessings be upon him) said: "Whoever sacrificed before the prayer should make another sacrifice in its place, and whoever has not yet sacrificed should sacrifice taking the name of Allah."
(b) In the narration of al-Saffar: When he (peace and blessings be upon him) learned of the people's sacrifices, he (peace and blessings be upon him) said: "Make other sacrifices in their place, and whoever has not yet sacrificed should sacrifice taking the name of Allah." From these hadiths it is known that a sacrifice made before the prayer will not be counted.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19117