Musnad Ahmad 330:4

Ya'qub narrated to us, he said: My father informed us, from Ibn Ishaq, who said: Muhammad ibn Muslim al-Zuhri mentioned, from Sa'id ibn al-Musayyib, from 'Abdullah ibn Zayd ibn 'Abd Rabbihi, who said: When the Messenger of Allah (peace and blessings of Allah be upon him) resolved to strike a bell to gather the people for prayer, and he disliked it because of its resemblance to the Christians, a visitor circled me at night while I was sleeping—a man wearing two green garments, and in his hand was a bell he was carrying. He said: I said to him, "O servant of Allah, will you sell the bell?" He said, "And what will you do with it?" I said, "We will call to prayer with it." He said, "Shall I not guide you to something better than that?" I said, "Yes." He said: "You say: Allah is the Greatest, Allah is the Greatest, Allah is the Greatest, Allah is the Greatest; I bear witness that there is no god but Allah, I bear witness that there is no god but Allah; I bear witness that Muhammad is the Messenger of Allah, I bear witness that Muhammad is the Messenger of Allah; Come to prayer, Come to prayer; Come to success, Come to success; Allah is the Greatest, Allah is the Greatest; There is no god but Allah." He said: Then he stepped back a short distance and said: "Then you say, when you establish the prayer: Allah is the Greatest, Allah is the Greatest; I bear witness that there is no god but Allah; I bear witness that Muhammad is the Messenger of Allah; Come to prayer; Come to success; The prayer has begun, The prayer has begun; Allah is the Greatest, Allah is the Greatest; There is no god but Allah." He said: When morning came, I went to the Messenger of Allah (peace and blessings of Allah be upon him) and informed him of what I had seen. The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, this is a true vision, if Allah wills." Then he commanded the Adhan, and Bilal, the freed slave of Abu Bakr, would call it, and he would call the Messenger of Allah (peace and blessings of Allah be upon him) to prayer. He said: So he came to him and called him one morning for the dawn prayer, and it was said to him: "The Messenger of Allah (peace and blessings of Allah be upon him) is sleeping." He said: So Bilal shouted at the top of his voice, "Prayer is better than sleep." Sa'id ibn al-Musayyib said: So this phrase was inserted into the Adhan for the dawn prayer.