1 John 4:20

If anyone says, "I love God," and hates his brother, he is a liar; for he that loves not his brother whom he has seen, cannot love God Whom he has not seen.

1 John 2:4

He who says, "I have known Him," and does not keep His commandments, is a liar, and the truth is not in him;

1 John 2:9

He who says that he is in the light, and hates his brother, is in the darkness even until now.

1 John 3:17

But whosoever possesses the goods of the world, and beholds his brother having need, and shuts up his compassion from him, how does the love of God abide in him?

1 John 4:12

No one has ever beheld God. If we love one another, God abideth in us, and His love has been perfected in us.

1 John 2:11

But he that hates his brother is in the darkness, and walks in the darkness, and knows not where he is going, because the darkness blinded his eyes.

1 Peter 1:8

Whom, not having seen, ye love; on Whom, though now not seeing Him, yet believing, ye exult with joy unspeakable and full of glory;

1 John 1:6

If we say that we have fellowship with Him, and are walking 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 have known Him," and does not keep His commandments, is a liar, and the truth is not in him;
1 John 3:17
But whosoever possesses the goods of the world, and beholds his brother having need, and shuts up his compassion from him, how does the love of God abide in him?

Not

1 John 4:12
No one has ever beheld God. If we love one another, God abideth in us, and His love has been perfected in us.

General references

Matthew 22:40
On these two commandments hangs the whole law, and the prophets."
Matthew 25:42
for I hungered, and ye did not give Me to eat; I thirsted, and ye gave Me no drink;
John 13:35
By this shall all know that ye are My disciples, if ye have love one to another."
John 14:15
"If ye love Me, ye will keep My commandments;
Hebrews 13:1
Let brotherly love continue.