The first Mu'adh-dhin in Islam was Bilal Ibn Rabah. He was a companion of the Prophet Muhammad (peace be upon him) and was chosen by him to be the first person to give the call to prayer (adhan) in Islam. Bilal was an Ethiopian slave who was freed by the Prophet and became one of his most trusted and loyal companions. He had a beautiful voice, which was why he was chosen for the important task of calling Muslims to prayer. The first time he gave the adhan, it was a historic moment in the early history of Islam. Bilal's adhan became a symbol of the unity of Muslims and is still recited by millions of Muslims around the world today.