Narrated Ibn 'Umar:
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....
Glory is to Allah and praise is to Him. (Recite one hundred times in Arabic).
Info: "Whoever recites this one hundred times in the morning and in the evening will not be surpassed on the Day of Resurrection by anyone having done better than this except for someone who had recited it more. " Al-Bukhari 4/2071.