Ibn Sirin محمد بن سيرين الأنصاري · The Book of the Prayer for the Two 'Eids

"I saw the Messenger of Allah (ﷺ) delivering the Khutbah standing up, then he sat down for a while and did not speak, then he stood up and delivered another Khutbah. Whoever tells you that the Prophet (ﷺ) delivered a Khutbah sitting do not believe him."