The Messenger of Allah ﷺ used to perform the prayers of the two Eids, al-Adha and al-Fitr, and then deliver the sermon after the prayer.
حدثنا حماد بن مسعدة عن عبيد الله عن نافع
أن رسول الله ﷺ كان يصلي العيدين الأضحى والفطر ثم يخطب بعد الصلاة
Its isnad is sahih. Hammad bin Masada Abu Saeed Basri is trustworthy, one of the teachers of Ahmad. Abu Hatim and Ibn Saad both regarded him as trustworthy, and Ibn Shahin said, "Trustworthy, trustworthy, there is no harm in him." Bukhari mentioned him in al-Kabir 1/2/25.The meaning of this hadith has come before many times, including at 4202 and 4394.