Musnad Ahmad 1153:2234

Yunus narrated to us, Hammad—meaning Ibn Salamah—narrated to us, from Budayl, from Abdullah ibn Shaqiq, from Aisha: "That the Messenger of Allah, peace and blessings of Allah be upon him, when he recited while standing, he would bow while standing, and when he recited while sitting, he would bow while sitting."