Musnad Ahmad 788:101

Waki’ narrated to us, Isra’il narrated to us, from Abu Ishaq, from Al-Aswad ibn Yazid, who said: Abu Musa Al-Ash’ari said: Ali, may Allah be pleased with him, reminded us of a prayer that we prayed with the Messenger of Allah, may Allah bless him and grant him peace. Either we had forgotten it, or we had abandoned it intentionally: "He would say the Takbir whenever he bowed, and when he prostrated, and when he rose."