1 John 4:20

If a man say I love God, and hateth his brother
Than which profession nothing can be more contradictory, not black and white, or hot and cold in the same degree:

he is a liar;
it is not truth he speaks, it is a contradiction, and a thing impossible:

for he that loveth not his brother whom he hath seen;
his person, which might have drawn out his affection to him; and something valuable and worthy in him, which might have commanded respect; or his wants and distresses, which should have moved his pity and compassion:

how can he love God whom he hath not seen?
it cannot be thought he should; the thing is not reasonable to suppose; it is not possible he should; (See Gill on 1 John 4:12).