Musnad Ahmad 32:1728

Ibrahim ibn Khalid narrated to us, he said: Umayyah ibn Shibl informed me, from Uthman ibn Yazdawayh, he said: I went out to Medina with Umar ibn Yazid, and Umar ibn Abd al-Aziz was the governor over it before he was made caliph. He said: So I heard Anas ibn Malik, and he had severe vitiligo, and he said: Umar used to lead us in prayer. Anas said: "I have not seen anyone whose prayer was more similar to the prayer of the Messenger of Allah, may Allah bless him and grant him peace, than this young man; he used to lighten [the prayer] while completing it."