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].
If a person says, “I love God,” yet [in reality] hates his brother, he is a liar. For the person who does not love his brother, whom he has seen, cannot [possibly] love God, whom he has never seen.
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].
But, anyone who lacks these qualities is [spiritually] blind and shortsighted, and has forgotten that he has been cleansed [i.e., forgiven] of his past sins.
The person who says, “I have come to know Him,” but does not obey what He commands, is lying [by such a profession], and the truth [about the matter] is not in his heart.
Jesus said to them, “If you were [really] blind [i.e., unable to see spiritually], you would not be guilty of sin. But since you claim, ‘We can see [fine],’ you remain guilty of sin.”
Here is how the children of God and the children of the devil can be recognized: All those who do not continue to do what is right do not belong to God. Also, the person who does not continue to love his brother [or sister does not belong to God].