1 John 4:20

If anyone says, I love God, and hates his brother, he is a liar. For if he 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 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 he is in the light and hates his brother is in darkness until now.

1 John 3:17

But whoever has this world's goods and sees his brother having need, and shuts up his bowels from him, how does the love of God dwell 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

But he who hates his brother is in darkness, and walks in darkness, and does not know where he is going, because darkness has blinded his eyes.

1 Peter 1:8

whom having not seen, you love; in whom not yet seeing, but believing in Him you exult with unspeakable joy, and having been glorified,

1 John 1:6

If we say that we have fellowship with Him and walk in darkness, we lie and do not practice 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 whoever has this world's goods and sees his brother having need, and shuts up his bowels from him, how does the love of God dwell 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 all the 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 all shall know that you are My disciples, if you have love toward one another.
John 14:15
If you love Me, keep My commandments.
Hebrews 13:1
Let brotherly love continue.