Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) narrates: When the Muslims came to Madinah Munawwarah, they used to gather at the time of prayer. They were not formally called for it. One day they discussed this matter, so someone said: You should ring a bell like the Christians’ bell. Some said: Blow a horn like the Jews. Then Sayyiduna Umar (may Allah be pleased with him) said:“Why don’t you send some people so that they may announce the prayer?”So the Noble Prophet (peace and blessings be upon him) said:“O Bilal! Stand up and give the adhan (call to prayer).”