He that saith. See on v. 4. John again appears to refer to heretical teachings, such as those of the Gnostics. He has already contrasted light with darkness chs. 1:5-7; 2:8 and truth with falsehood chs. 1:8—10; 2:4. Now he deals similarly with love and hate (ch. 2:9-11).
In the light. The state of those who are truly “in the light” is implied in ch. 1:5-7 (see comment there).
Hateth. Nothing is said about the degree of hatred. It can exist as a state of passive “nonloving,” as an active dislike, or as a malignant hate that seeks to harm its object. The slightest trace of hatred is sufficient to show that the God of love does not have full sway in the heart (Matt. 5:21, 22; MB 55-58).
Brother. Except when specifying family relationship, the word “brother” in the writings of John usually refers to a member of the Christian church. Though hatred of anyone would mean that a man is in darkness, John is particularly concerned with Christian relationships.
Darkness. See on ch. 1:5. He who claims spiritual enlightenment yet harbors hatred for a fellow believer clearly demonstrates that he is dwelling in spiritual darkness even “until now,” that is, at the very moment he makes the false claim.