He had slaughtered his sacrifice before the Messenger of Allah ﷺ went out for the prayer. He mentioned this to the Messenger of Allah ﷺ after he had finished, and the Messenger of Allah ﷺ commanded him to repeat his sacrifice.
حدثنا يزيد بن هارون أخبرنا يحيى يعني ابن سعيد أن عباد بن تميم أخبره
أنه ذبح قبل أن يغدو رسول الله ﷺ وأنه ذكر ذلك لرسول الله ﷺ بعدما فرغ فأمره رسول الله ﷺ أن يعود لأضحيته