Musnad Ahmad 32:1363

Fazara ibn Umar and Yunus ibn Muhammad narrated to us, they said: Fulayh narrated to us, from Muhammad ibn Musahiq, from Amir ibn Abdullah, from Anas, who said: "I have not seen an Imam whose prayer was more similar to the prayer of the Messenger of Allah, peace and blessings of Allah be upon him, than your Imam, Umar ibn Abd al-Aziz." He said: "And Umar would not prolong the recitation."