'In the Darkness' in the Bible

The person who claims to be living in [harmony with] the light [i.e., by obeying God's truth], and [yet] hates his brother is still [living] in the darkness [of sin].

But the person who hates his brother is in the darkness [of sin] and he lives in [harmony with] that darkness, and he does not know where he is heading, because the darkness [of sin] has blinded his eyes [to his spiritual condition].