1 John 4:20

If any man says, I love God, and hates his brother, he is a liar. For he who does not love his brother whom he has seen, how can he love God whom he has not seen?

1 John 2:4

He who says, I know him, and does not keep his commandments, is a liar, and the truth is not in this man.

1 John 2:9

He who claims to be in the light, and hates his brother, is in the darkness until now.

1 John 3:17

But whoever has the world's living, and sees his brother having need, and closes his bowels from him, how does the love of God abide in him?

1 John 4:12

No man has ever seen God. If we love each other, God abides in us, and his love is in us, having been fully perfected.

1 John 2:11

But he who hates his brother is in the darkness, and he goes about in the darkness, and knows not where he goes, because the darkness has blinded his eyes.

1 Peter 1:8

Whom, not having seen, ye love, in whom, not now seeing but believing, ye exult in inexpressible and glorified joy,

1 John 1:6

If we say that we have fellowship with him and walk in the darkness, we lie, and do not the truth.

Treasury of Scripture Knowledge

Summary

If a man say, I love God, and hateth his brother, he is a liar: for he that loveth not his brother whom he hath seen, how can he love God whom he hath not seen?

Bible References

A man

1 John 2:4
He who says, I know him, and does not keep his commandments, is a liar, and the truth is not in this man.
1 John 3:17
But whoever has the world's living, and sees his brother having need, and closes his bowels from him, how does the love of God abide in him?

Not

1 John 4:12
No man has ever seen God. If we love each other, God abides in us, and his love is in us, having been fully perfected.

General references

Matthew 22:40
On these two commandments hang all the law, and the prophets.
Matthew 25:42
For I was hungry, and ye did not give me to eat, I was thirsty, and ye gave me no drink,
John 13:35
By this all men will know that ye are my disciples, if ye have love among each other.
John 14:15
If ye love me, keep my commandments.
Hebrews 13:1
Let brotherly love abide.