1 John 4:20

If a man sayeth, 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?

1 John 2:4

He that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him.

1 John 2:9

He that saith he is in the light, and hateth his brother, is in darkness even until now.

1 John 3:17

But he who hath this world's good, and seeth his brother have need, and shutteth up his bowels of compassion from him, how dwelleth the love of God in him?

1 John 4:12

No man hath seen God at any time. If we love one another, God dwelleth in us, and his love is perfected in us.

1 John 2:11

But he that hateth his brother is in darkness, and walketh in darkness, and knoweth not whither he goeth, because darkness hath blinded his eyes.

1 Peter 1:8

Whom having not seen, ye love; in whom, though now ye see him not, yet believing, ye rejoice with joy unspeakable, and full of glory:

1 John 1:6

If we say that we have fellowship with him, and walk in 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 that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him.
1 John 3:17
But he who hath this world's good, and seeth his brother have need, and shutteth up his bowels of compassion from him, how dwelleth the love of God in him?

Not

1 John 4:12
No man hath seen God at any time. If we love one another, God dwelleth in us, and his love is perfected in us.

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 gave me no food: I was thirsty, and ye gave me no drink:
John 13:35
By this shall all men know that ye are my disciples, if ye have love one to another.
John 14:15
If ye love me, keep my commandments.
Hebrews 13:1
Let brotherly love continue.