One of the early companions who sacrificed for the sake of Allah (SWT) was Hamamah Al-Habashiyyah (RA).
Hamamah was born in Abyssinia as a free person but was later enslaved by a man from Quraysh. While enslaved, she was able to marry Rabah, who was an Arab.
It is narrated that Abu ‘Umar stated in Al-Isbah by ibn Hajar Al-Asqalani that Hamamah was torture because of her belief in Allah (SWT), thus is a testimony that she was recognized as being Muslim. She was freed from slavery by Abu Bakr.
Abu Ali Al-Ghassani stated that this woman of honor was the mother of Bilal the Prayer Caller (RA), who the Prophet (SAWS) gave the title Master of the Prayer Callers (Sayyid Al-Mu’adhdhinin).
Weblog of Dawud Walid 