Musannaf Ibn Abi Shayba 2:45

Abu Bakr narrated to us, he said: Abda narrated to us, from Muhammad ibn Ishaq, from al-Zuhri, from Sa'id ibn al-Musayyib, who said: Bilal came to the Prophet, may Allah bless him and grant him peace, to inform him of the prayer, and it was said to him that he was sleeping. So Bilal shouted at the top of his voice, "Prayer is better than sleep," and it was inserted into the Adhan.