'Twas mercy brought me from my Pagan land,
Taught my benighted soul to understand
That there's a God, that there's a Saviour too:
Once I redemption neither sought nor knew.
Some view our sable race with scornful eye,
Phillis Wheatley refers to her life before she was brought to America as benighted. Benighted means being overtaken by darkness, which in this context refers to sin. 
 It can also mean a life without the knowledge of God (ignorance), or as Christians would put it, a life of sin. She has come to embrace Christianity more than her previous religion back in Africa. 
 This imagery of darkness invoked here by the word  “benighted”  isn’t accidental. Wheatley is well aware that the darkness of her skin is an excuse, a pretext, or otherwise a reason for white people to pre-judge her moral character. To slave-owners, black people were dark and dumb inside and out. Through the poem, she seeks to dissociate the moral darkness for the physical appearance. 
 In “The Difficult Miracle of Black Poetry in America,” poet June Jordan points out how Phillis Wheatley “clearly reverses what had happened to that African child, surrounded by and captured by the greed of white men.” While Jordan doesn’t cut Phillis Wheatley any slack for “her bizarre interpretation of slavery’s theft of Black life as a merciful rescue,” Jordan suggests that these facts “should not bewilder anyone”: “These are regular kinds of iniquitous nonsense found in white literature, the literature that Phillis Wheatley assimilated, with no choice in the matter.”
On Being Brought from Africa to America