Bilal was originally from Abyssinia and in Madinah, was one of the slaves of the tribe of Bani Jama.’ After he had embraced Islam he had to suffer intense hardships at the hands of his owners.
During the onset of Islam those in Mecca who had embraced the faith had to face great adversities – especially those, who did not possess any familial or tribal support, or were slaves and servants. Some, due to the intensity of sufferings, even backtracked from their (new) religion but Bilal exhibiting great patience, increased in steadfastness as thus, his owners increased their torture upon him.
Abu Jahl would force him to lie on his stomach on the hot sands of Hijaz, pin him down by means of a millstone till his brains would almost come to a boil due to the intensity of the heat and then say to him: “Deny the Allah of Muhammad!” However, all that Bilal would say was: “Ahad Ahad” – meaning Allah is One.
One of those, who greatly persecuted him, was Umayyah Ibn Khalaf, who used to torture him repeatedly. However, as Divine decree would have it, he was killed in the battle of Badr at the hands of Bilal.
During one of those occasions when Bilal was being tortured, the Noble Prophet (s.a.w) happened to pass by. Witnessing him, he (s.a.w) said to Abu Bakr: “Had I possessed money, I would have purchased Bilal.” Later he (s.a.w) approached his uncle Abbas and said: “Purchase Bilal for me.” Even as Abbas went in search of the woman who owned him, Bilal was being subjected to torture and persecution – pinioned under the weight of heavy stones and almost on the verge of death.
Abbas approached the woman and expressed his desire to purchase Bilal whereupon she began to criticize and speak ill of him, but eventually sold him. Thus, Bilal, as a result of his patience in the face of torture and persecution, became free and entering into the services of the Noble Prophet (s.a.w) he became his muezzin. ( Paighambar Wa Yaran, vol. 2, pg. 66; Asad al-Ghabbah, vol. 1, pg. 206 )