Musnad Ahmad 658:44

Muhammad ibn Ja'far narrated to us, he said: Shu'bah narrated to us, he said: I heard Abu Ishaq narrating that he heard Abdullah ibn Yazid al-Ansari delivering a sermon, and he said: Al-Bara' informed us—and he is not a liar—"that the Messenger of Allah, peace and blessings of Allah be upon him, when he would raise his head from bowing, they would stand upright until he prostrated, then they would prostrate."