From Sahih Bukhari (Hadith 951):
Narrated Al-Bara':I heard the Prophet (ﷺ) delivering a Khutba saying, "The first thing to be done on this day (first day of `Id ul Adha) is to pray; and after returning from the prayer we slaughter our sacrifices (in the name of Allah) and whoever does so, he acted according to our Sunna (traditions)
Reference: Bukhari 951