Musnad Ahmad 33:19

'Abd al-Razzaq narrated to us, Ibn Jurayj informed us, Abu al-Zubayr informed me that he heard Jabir ibn 'Abd Allah saying: "The Prophet (peace and blessings of Allah be upon him) led us in prayer on the Day of Sacrifice (Yawm al-Nahr) in Medina. Some men stepped forward and slaughtered [their sacrifices], thinking that the Prophet (peace and blessings of Allah be upon him) had already slaughtered. So he ordered whoever had slaughtered before him to repeat it with another sacrifice, and [he ordered them] not to slaughter until the Prophet (peace and blessings of Allah be upon him) had slaughtered."