Sunan Ibn Majah
1105
Sahih+3

It was narrated that Simak bin Harb said:“I heard Jabir bin Samurah say: ‘The Messenger of Allah (ﷺ) used to deliver the sermon standing, but he used to sit down briefly, then stand up.’”

SahihAl-Albani
SahihMuhammad Fouad Abd al-Baqi