Musnad Ahmad 907:12

Umar ibn Sa'd Abu Dawud al-Hafari narrated to us, from Sufyan, from Simak, from Jabir ibn Samurah, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) used to deliver the sermon while standing, and he would sit between the two sermons, and he would recite verses, and he would remind the people."