That he witnessed the Prophet (ﷺ) on the Day of Nahr. The Prophet (ﷺ) offered prayer and then delivered a sermon saying, "Whoever slaughtered his sacrifice before offering prayer, should slaughter another animal in place of the first; and whoever has not yet slaughtered any, should slaughter a sacrifice and mention Allah's Name while doing so."
Reference: Sahih al-Bukhari 7400 In-book : Book 97, Hadith 29 USC-MSA web (English) : Vol. 9, Book 93, Hadith 497 (deprecated)
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