(Imām Bukhārī narrates): 'Ubaidullah bin 'Umar al-Qawariri narrated to us, he said: Khalid bin al-Harith narrated to us, he said: 'Ubaidullah bin 'Umar narrated to us from Nafi' from Hadhrat Ibn 'Umar (may Allāh be pleased with them both), he said,
"The Prophet ﷺ used to deliver the khutbah standing, then he would sit, then he would stand, just as you do now."
Reference: Sahih Al Bukhari 920