Sayyiduna Ibn Umar (may Allah be pleased with them both) narrates that when the Muslims came to Madinah Munawwarah, they would simply gather together and fix a time for prayer, but no one would call them. Then one day they discussed this matter, so some of them said: Make a bell like the Christians’ bell, while others said: Make a horn like the Jews’ horn. Sayyiduna Umar (may Allah be pleased with him) said: Why don’t you send a man to announce the prayer? So the Messenger of Allah (peace and blessings be upon him) said:“O Bilal, get up and announce the prayer.”