Do you know who Bilal ibn Rabah (RA) is?
Bilal ibn Rabah (RA) is known for being the chief of all muaddhins. His parents were both prominent before becoming slaves. Bilal (RA)'s father was Arab and his mother, Hamama, was a princess in Abyssinia. They were taken as slaves during the year of the elephant. Thus Bilal (RA) grew up as a slave in the Arab world.
Known for his strength and intelligence, he fell into the hands of Ummayyah ibn Khalaf - one of the staunchest enemies of Islam.
Bilal (RA) accepted Islam, and would say “ahadun ahad” - “One God”, even as he was being tortured. When Umar ibn al-Khattab (RA) asked him why he only said ahadun ahad, Bilal (RA) responded, “Oh commander of the believers, had I known anything other than One, I would have said it. That was all I knew about Allah (SWT)”. And for those words, Bilal (RA) was tortured, almost to death.
Bilal (RA) was freed by Abu Bakr (RA) for a huge price. Later on Umar ibn al Khattab (RA) would call Bilal ibn Rabah (RA) Sayyidunaa and ”our master who was freed by our master”.
Bilal (RA) is known as the chief of all muadhins - he was the first to give the adhan in Madinah, and then in the Kaba, after the conquest of Mecca.