I have previously written an answer to a similar question which I have revised and slightly updated for you.
Ayuba Suleiman Diallo was a Fulbe Muslim, born in the kingdom of Bondu in 1701. In 1730, Diallo was captured near the Gambia river during a trade mission where he was, ironically, trading enslaved persons. He and his companion and interpreter, Loumein Yoas, were promptly sold into slavery. Diallo survived crossing Atlantic on the slave ship Arabella and was forced to be a laborer on a tobacco plantation in Maryland where he would work for the next two years. Diallo successfully escaped from the plantation, but found himself being imprisoned since he could not identify who he was and was not carrying any sort of identification or pass from his enslaver. While in prison, he met attorney Thomas Bluett, who saw him for what he really was: a literate man, who could both speak and write Arabic well. Not only that, he came from a prominent clerical family.
Thomas Bluett himself wrote about his first impressions:
He was brought into the Tavern to us, but could not speak one Word of English. Upon our Talking and making Signs to him, he wrote a Line or two before us, and when he read it, pronounced the Words Allah and Mahommed; by which, and his refusing a Glass of Wine we offered him, we perceived he was a Mahometan [Muslim], but could not imagine of what Country he was or how he got thither; for by his affable Carriage and the easy Composure of his Countenance, we could perceive he was no common Slave.
Although Diallo was forced to return to his life of slavery, Bluett helped him to regain his freedom together with other individuals who felt compassionate about his situation. His enslaver was eager to get rid of Diallo since he saw no place for Diallo at the plantation. Diallo had been unable to handle the manual labor during his time on the plantation and was instead given lighter work watching cattle. [He] would often leave the Cattle and withdraw into the Woods to pray; but a white Boy frequently watched him, and whilst he was at his Devotion would mock him and throw Dirt in his Face.
Therefore, after what had been revealed about him, Diallo's enslaver sold his freedom willingly and Diallo was finally emancipated in England which he had traveled to together with Bluett in 1733. While in England, Diallo even got the opportunity to meet the Queen of England whom according to Bluett presented him with a "rich Gold Watch." Diallo ultimately returned home to Bondu a year later in 1734. In the words of Bluett: About the latter End of July last he embark’d on Board one of the African Company’s Ships, bound for Gambia, where we hope he is safely arrived, to the great Joy of his Friends, and the Honour of the English Nation. His interpreter, Loumein Yoas, remained enslaved in Maryland until 1738 until he too managed to gain his freedom, thanks to Diallo and Bluett.
Bluett published Diallo's story (and his own) in Some Memories of the Life of Job, the Son of the Solomon High Priest of Boonda in Africa; Who was enslaved about two Years in Maryland; and afterwards being brought to England, was set free, and sent to his native Land in the Year 1734 which is considered one of the earliest slave narratives of the Atlantic slave trade.
This portrait was painted by William Hoare of Bath in 1733 during Diallo's stay in England. He is depicted wearing the Qu'ran strung from his neck. The portrait can now be seen in the National Portrait Gallery in London.