Narrated by Al-Bara’:
I heard the Prophet (p.b.u.h) 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).”
[Bukhari Vol 2 Book 15 Hadith 71]