Musannaf Ibn Abi Shaybah 3553 — Informing the imam and the ruler

Mughirah said: When people were slow in coming to the prayer, the muezzin would say these words: "Ashhadu anna Muhammadan rasul Allah, qad qamat al-salah, qad qamat al-salah, hayya 'ala al-salah, hayya 'ala al-salah, hayya 'ala al-falah, hayya 'ala al-falah (I bear witness that Muhammad is the Messenger of Allah; the prayer has begun, the prayer has begun; come to prayer, come to prayer; come to success, come to success)."