When the Muslims arrived at Medina, they used to assemble for the prayer, and used to guess the timefor it. During those days, the practice of Adhan for the prayers had not been introduced yet. Once theydiscussed this problem regarding the call for prayer. Some people suggested the use of a bell like theChristians, others proposed a trumpet like the horn used by the Jews, but `Umar was the first tosuggest that a man should call (the people) for the prayer; so Allah's Messenger (ﷺ) ordered Bilal to get upand pronounce the Adhan for prayers.