Sunan An-Nasai, Chapter: The Book of the Adhan (The Call to Prayer)

"I used to call the Adhan for the Messenger of Allah (saw) and in the first Adhan of Fajr I used to say: 'Hayya 'ala al-falah, as-salatu khairun minan-nawm, as-salatu khairun minan-nawm, Allahu Akbar Allahu Akbar, la ilaha illallah (Come to prosperity, prayer is better than sleep, prayer is better than sleep, Allah is the Greatest, Allah is the Greatest, there is non worthy of worship except Allah).'" (Sahih)