Bilal Ibn Rajah was a slave who used to survive on only a handful of dates. His owner Umayyah ibn Khallaf overworked and mistreated Bilal as well as his other slaves.
Bilal heard about Prophet Muhammad (sallalahu alaihi was sallam) and Islam when he overheard conversations between his master and guests talking about Prophet Muhammad (sallalahu alaihi was sallam). He also heard Abu Bakr talking about Islam and eventually he went with Abu Bakr to Prophet Muhammad (sallalahu alaihi was sallam) to announce his acceptance of Islam, the seventh person to do so.
Bilal’s acceptance of Islam caused Umayyah to treat him even more harshly. He would force Bilal to go out during the hottest part of the day wearing armor where he would be face down in the sand. He would also have an enormous rock placed on his chest and Umayyah would tell him to either die or denounce Prophet Muhammad (sallalahu alaihi was sallam) and worship the idols he did. Bilal would refuse continually saying, "Ahad" (One). Abu Bakr happened to pass by one day and observed this happening. He chastised Umayyah for his treatment of Bilal, whereupon Umayyah told him he was the reason that Bilal was the way he was (i.e. worshipping Allah alone). Abu Bakr told Umayyah to name his price for Bilal, which Umayyah readily accepted. Umayyah was harsh even in his selling of Bilal stating he would have sold him for only an ounce of gold, to which Abu Bakr stated he would have got Bilal for even a hundred ounces of gold. Abu Bakr and Bilal went to the Prophet Muhammad (sallalahu alaihi was sallam) where Abu Bakr announced he was freeing Bilal.
Once the Muslims were in Madinah, they were thinking about ways to call people for the prayer. Abdullah Ibn Zayd and came to Prophet Muhammad (sallalahu alaihi was sallam) telling him about a dream he had. He said a man wearing two green garments came to him holding a bell, which Abdullah offered to buy. When he asked him what he (Abdullah) wanted it for, he told him it was for calling people to the prayer. He then told Abdullah of a better way (to call people to the prayer. It was to say Allahu Akbar four times, Ash-hadu-allaa-ilaaha-illa-Allah two times, Ash-hadu-anna-Muhammadar-Rasoolullah two times, Haya-alas-salah twice, Haya-alal-falah twice, Allahu Akbar twice, and then Laa-ilaaha-illa-Allah once. Prophet Muhammad (sallalahu alaihi was sallam) told him it was a true vision and told him to teach Bilal it because of his beautiful and far reaching voice. Bilal was the first person to utter the adhan. When Umar bin Khattab heard the adhan he ran to Prophet Muhammad (sallalahu alaihi was sallam) telling him he also had the dream about the adhan. Prophet Muhammad (sallalahu alaihi was sallam) told him the revelation had already preceded him.
During the Battle of Badr many members of the Quraysh were taken as prisoners, among them was Umayyah. When Bilal saw him he cried out, "The arch-enemy of Allah, Umayyah ibn Khalaf! May I not live if he lives!" Because Bilal kept repeating these words, one of the other companions killed Umayyah with his sword.
Bilal was indeed very pious. He offer two rakat (units) of prayer whenever he completed his wudhu. He had a great love for Prophet Muhammad (sallalahu alaihi was sallam). When Prophet Muhammad (sallalahu alaihi was sallam) passed away, Bilal was asked to make the adhan, when he got to the name of Prophet Muhammad (sallalahu alaihi was sallam) he could not continue because he was sobbing so heavily. He declared he would not call the adhan anymore.
When Abu Bakr was the Khalifah, Bilal went to the ash-Sham area for jihad and he spent the rest of his life there. He only made the adhan twice after that, once when Umar bin Khattab came to the ash-Sham area and the second when he went back to Madinah to the tomb of Prophet Muhammad (sallalahu alaihi was sallam). His voice caused the people to cry since it reminded them of the days when Prophet Muhammad (sallalahu alaihi was sallam) was alive.
Bilal died at the age of sixty-four living behind a legacy of extreme dedication to the worship of Allah.