Explanation

Hazrat Abu Bakr (RA) freed Hazrat Bilal (RA) from slavery.

Bilal (RA) was a slave of Umayyah ibn Khalaf, a harsh master who tortured Bilal for embracing Islam.

Abu Bakr (RA) purchased and freed Bilal, who later became a prominent companion of the Prophet Muhammad (SAW) and a renowned mu'adhin (caller to prayer).