The Prophet (ﷺ) used to deliver the Khutbah (religious talk, sermon) while standing. He (ﷺ) would then sit down and then stand up and deliver the Khutbah in a standing posture. So, whoever informs you that he [the Prophet (ﷺ)] delivered the Khutbah (religious talk, sermon) while sitting has definitely told a lie.[Reported by Muslim].