What does the Bible say about sin's impact on our nature?

In Scripture, sin is depicted as having a profound effect on our being, causing spiritual blindness and rendering us corrupt according to Ephesians 4:17-19. The Shulamite woman in Song of Solomon labors under the reality of her blackness, a metaphor for her sinful condition, stating, 'I am black, but comely.' This acknowledges that while we are inherently sinful and under the domain of darkness (Ephesians 5:8), it is through grace that we can recognize our need for God's redemptive power.