Allah is most great. I witness that there is no god beside Allah. I witness that Muhammad is the messenger of Allah.
Prayer is better than sleep.
There is no god beside Allah. When the Muslims arrived at Medina, they used to assemble for the prayer, and used to guess the time for it. During those days, the practice of Adhan for the prayers had not been introduced yet. Once they discussed this problem regarding the call for prayer. This also indicates that the practice of Adhan is a human invention.