1 John 4:20

If any one saith, 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 the darkness until now.

1 John 3:17

But whoever hath this worlds goods, and seeth his brother having need, and shutteth up his compassion from him, how dwelleth the love of God in him?

1 John 4:12

No one hath ever seen God. 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 the darkness, and walketh in the darkness, and knoweth not whither he goeth, because the 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 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 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 whoever hath this worlds goods, and seeth his brother having need, and shutteth up his compassion from him, how dwelleth the love of God in him?

Not

1 John 4:12
No one hath ever seen God. 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 will all men know that ye are my disciples, if ye have love one for another.
John 14:15
If ye love me, ye will keep my commandments;
Hebrews 13:1
Let brotherly love continue.