1 John 4:20

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

1 John 2:4

Whoever says, "I know him," but does not obey his commands, is a liar, and there is no truth in his heart;

1 John 2:9

Whoever says, "I am in the light," and yet hates his brother, is still in darkness.

1 John 3:17

But if someone who is rich sees his brother in need and closes his heart against him, how can he have any love for God in his heart?

1 John 4:12

No one has ever seen God; yet if we love one another, God keeps in union with us and love for him attains perfection in our hearts.

1 John 2:11

But whoever hates his brother is in darkness, and is living in darkness, and he does not know where he is going, for the darkness has blinded his eyes.

1 Peter 1:8

You must love him, though you have not seen him, but since you believe in him though you do not now see him, rejoice with triumphant, unutterable joy

1 John 1:6

If we say, "We have fellowship with him," and yet live in darkness, we are lying and not living 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
Whoever says, "I know him," but does not obey his commands, is a liar, and there is no truth in his heart;
1 John 3:17
But if someone who is rich sees his brother in need and closes his heart against him, how can he have any love for God in his heart?

Not

1 John 4:12
No one has ever seen God; yet if we love one another, God keeps in union with us and love for him attains perfection in our hearts.

General references

Matthew 22:40
These two commands sum up the whole of the Law and the Prophets."
Matthew 25:42
For when I was hungry, you gave me nothing to eat, and when I was thirsty you gave me nothing to drink,
John 13:35
By this they will all know that you are my disciples??y your love for one another."
John 14:15
"If you really love me, you will observe my commands.
Hebrews 13:1
Your love for the brotherhood must continue.