Albert Barnes' Notes on the Whole Bible - 1 John 4:20
If a man say, I love God, and hateth his brother - His Christian brother; or, in a larger sense, any man. The sense is, that no man, whatever may be his professions and pretensions, can have any true love to God, unless he loves his brethren.He is a liar - Compare the notes at 1 John 1:6. It is not necessary, in order to a proper interpretation of this passage, to suppose that he “intentionally” deceives. The sense is, that this must be a false profession.For he that loveth not his brother whom... read more
The Pulpit Commentary - 1 John 4:20-21
Love to man the expression of love to God. Connecting link: The apostle has just declared that the love which pervades believers is owing to God's love to them. He now advances to another and, indeed, to the final step in this paragraph on love, in which he sets forth more powerfully than ever the truth which he has thrice before ( 1 John 3:10 , 1 John 3:17 ; 1 John 4:8 £ ) indicated, that love to God and love to man are inseparably connected together; that if any man declares... read more