Musnad Abu Ya'la al-Mawsili 151:68

Abu Bakr narrated to us, Ibn Abi Ghaniyah narrated to us, from al-A'mash, from Ibrahim, from 'Alqamah, from 'Abdullah, that he was asked: "Did the Prophet, may Allah bless him and grant him peace, deliver the sermon while standing?" He said: "Yes." Then he recited: "And they left you standing" (al-Jumu'ah: 11).