Maliks Muwatta Book 023, Hadith Number 005.

Section : Prohibition against Sacrificing an Animal Before the Imam Departs.

Yahya related to me from Malik from Yahya ibn Said from Abbad ibn Tamin that one time Uwaymir ibn Ashqar sacrificed his animal before the prayer on the morning of the Day of Sacrifice, and he mentioned that the Messenger of Allah, may Allah bless him and grant him peace, had ordered him to sacrifice another animal.