1 John 4:20

If any man say, I love God, and yet hate his brother, he is a liar: for he that loves not his brother, whom he has seen, how can he love God whom he has not seen?

1 John 2:4

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

1 John 2:9

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

1 John 3:17

Whoever has this world's goods, and sees his brother have need, and shuts his heart against him, how dwells the love of God in him?

1 John 4:12

No one has seen God at any time. If we love one another, God dwells in us, and his love is perfected in us.

1 John 2:11

He that hates his brother is in darkness, and walks in darkness; and he knows not whither he goes, because darkness has blinded his eyes.

1 Peter 1:8

-whom, though you have not seen him, yet you love; on whom not now looking, but believing, you 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 says, I know him, and keeps not his commandments, is a liar, and the truth is not in him.
1 John 3:17
Whoever has this world's goods, and sees his brother have need, and shuts his heart against him, how dwells the love of God in him?

Not

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

General references

Matthew 22:40
On these two commandments hang the whole law and the prophets.
Matthew 25:42
For I was hungry, and you gave me no food; I was thirsty, and you gave me no drink;
John 13:35
By this shall all men know that you are my disciples, if you have love one for another.
John 14:15
If you love me, keep my commandments;
Hebrews 13:1
Let brotherly love continue.