Musannaf Ibn Abi Shayba 2:42

Abu Bakr narrated to us, he said: Abda bin Sulayman narrated to us, from Hisham bin Urwa, from a man who is called Ismail, he said: The mu'adhdhin came to Umar for the morning prayer and said, "Prayer is better than sleep." Umar was pleased with it and said to the mu'adhdhin, "Establish it in your adhan."