The Apostle of Allah (ﷺ) gave two sermons between which he sat, recited the Qur'an and exhorted the people.
Sahih Muslim Book 7, Hadith 45
← Previous Hadith Ibn 'Umar said that the Messenger of Allah (ﷺ) used to deliver the sermon on Friday while standing. He would then sit and then stand (for the second sermon) as they (the Muslims) do nowadays.

Sahih Muslim Book 7, Hadith 44 Next Hadith → Jabir b. Samura said that the Messenger of Allah (ﷺ) used to deliver the sermon while standing. He would then sit down and then stand up and address in a standing posture; and whoever informed you that he (the Holy Prophet) delivered the sermon while sitting told a lie. By Allah. I prayed with him more than two thousand times.

Sahih Muslim Book 7, Hadith 46