Musnad Ahmad 32:1776

Surayj narrated to us, Fulayh narrated to us, from Muhammad ibn Musahiq, from Amir ibn Abdullah, who said: Anas ibn Malik said: "I have not seen an imam whose prayer was more similar to the prayer of the Messenger of Allah, may Allah bless him and grant him peace, than this imam of yours." He said: "And Umar—meaning Ibn Abd al-Aziz—would not prolong the recitation."