1 John 4:20

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, cannot love God whom he hath not seen.

1 John 2:4

He that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him;

1 John 2:9

He that saith he is in the light and hateth his brother, is in the darkness even until now.

1 John 3:17

But whoso hath the world's goods, and beholdeth his brother in need, and shutteth up his compassion from him, how doth the love of God abide in him?

1 John 4:12

No man hath beheld God at any time: if we love one another, God abideth in us, and his love is perfected in us:

1 John 2:11

But he that hateth his brother is in the darkness, and walketh in the darkness, and knoweth not whither he goeth, because the darkness hath blinded his eyes.

1 Peter 1:8

whom not having seen ye love; on whom, though now ye see him not, yet believing, ye rejoice greatly with joy unspeakable 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 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 saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him;
1 John 3:17
But whoso hath the world's goods, and beholdeth his brother in need, and shutteth up his compassion from him, how doth the love of God abide in him?

Not

1 John 4:12
No man hath beheld God at any time: if we love one another, God abideth in us, and his love is perfected in us:

General references

Matthew 22:40
On these two commandments the whole law hangeth, and the prophets.
Matthew 25:42
for I was hungry, and ye did not give me to eat; I was thirsty, and ye gave me no drink;
John 13:35
By this shall all men 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 love of the brethren continue.

American Standard Version Public Domain