1 John 4:20

If a man says, "I love God," and hates his brother, he is a liar; for he who does not love his brother whom he has seen, cannot love God whom he has not seen.

1 John 2:4

One who says, "I know 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 the darkness even until now.

1 John 3:17

But whoever has the world's goods, and sees his brother in need, and closes his heart of compassion against him, how does the love of God remain in him?

1 John 4:12

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

1 John 2:11

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

1 Peter 1:8

whom not having seen you love; in whom, though now you do not see him, yet believing, you rejoice greatly with joy inexpressible 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 tell 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
One who says, "I know him," and does not keep his commandments, is a liar, and the truth is not in him.
1 John 3:17
But whoever has the world's goods, and sees his brother in need, and closes his heart of compassion against him, how does the love of God remain in him?

Not

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

General references

Matthew 22:40
The whole Law and the Prophets depend on these two commandments."
Matthew 25:42
for I was hungry, and you did not give me food to eat; I was thirsty, and you gave me no drink;
John 13:35
By this everyone will know that you are my disciples, if you have love for one another."
John 14:15
If you love me, you will keep my commandments.
Hebrews 13:1
Let brotherly love continue.