Musnad Abu Ya'la al-Mawsili 108:162

Abu Bakr narrated to us, Humayd ibn Abd al-Rahman narrated to us, from his father, from Abu al-Zubayr, from Jabir: That Abu Bakr used to pray by the prayer of the Messenger of Allah (may Allah bless him and grant him peace), and the people used to pray by the prayer of Abu Bakr.