Passage
Every one who is hating his brother--a man-killer he is, and ye have known that no man-killer hath life age-during in him remaining,
Every one who is hating his brother--a man-killer he is, and ye have known that no man-killer hath life age-during in him remaining,
1 John 3:13 Do not wonder, my brethren, if the world doth hate you;
1 John 3:14 we--we have known that we have passed out of the death to the life, because we love the brethren; he who is not loving the brother doth remain in the death.
1 John 3:15 Every one who is hating his brother--a man-killer he is, and ye have known that no man-killer hath life age-during in him remaining,
1 John 3:16 in this we have known the love, because he for us his life did lay down, and we ought for the brethren the lives to lay down;
1 John 3:17 and whoever may have the goods of the world, and may view his brother having need, and may shut up his bowels from him--how doth the love of God remain in him?
The verse centers on "hating", "brother--a", "man-killer", "known", "hath", "life", and "age-during". It is saying that the verse draws attention to "hating" and "brother--a", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 14's "we--we have known that we have passed..." into verse 16's "in this we have known the love...", so "hating" and "brother--a" belong inside that flow. In 1 John context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "hating" and "brother--a" with trust shaped by these words, not by a vague optimism outside the passage.