Musnad Ahmad 32:718

Abdullah ibn Ibrahim ibn Umar ibn Kaysan narrated to us, he said: My father informed me, from Wahb ibn Manus, from Sa'id ibn Jubayr, from Anas ibn Malik, who said: "I have not seen anyone more similar in prayer to the Messenger of Allah, may Allah bless him and grant him peace, than this young man"—meaning Umar ibn Abd al-Aziz. He said: "So we estimated ten glorifications in the bowing (ruku'), and ten glorifications in the prostration (sujud)."