1 John 4:20

If a man say, "I love God," and yet hate his brother, he is a liar. For how can he that loveth not his brother whom he hath seen, love God whom he hath not seen?

1 John 2:4

He that saith, "I know him," and yet keepeth not his commandments, is a liar, and the verity is not in him.

1 John 2:9

He that saith how that he is in the light, and yet hateth his brother, is in darkness even until this time.

1 John 3:17

He, then, that hath the substance of the world, and seeth his brother have need, and shutteth up his compassion from him: how dwelleth the love of God in him?

1 John 4:12

No man hath seen God at any time. If we love one another, God dwelleth in us, and his love is perfect in us.

1 John 2:11

And he that hateth his brother is in darkness, and walketh in darkness; and knoweth not whither he goeth, for darkness hath blinded his eyes.

1 Peter 1:8

whom ye have not seen and yet love him, in whom even now, though ye see him not, yet ye believe, and rejoice with joy unspeakable and glorious:

1 John 1:6

If we say that we have fellowship with him, and yet 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 saith, "I know him," and yet keepeth not his commandments, is a liar, and the verity is not in him.
1 John 3:17
He, then, that hath the substance of the world, and seeth his brother have need, and shutteth up his compassion from him: how dwelleth the love of God in him?

Not

1 John 4:12
No man hath seen God at any time. If we love one another, God dwelleth in us, and his love is perfect in us.

General references

Matthew 22:40
In these two commandments, hang all the law and the prophets."
Matthew 25:42
For I was a hungered, and ye gave me no meat. I thirsted, and ye gave me no drink. I was harborless, and ye lodged me not.
John 13:35
By this shall all men know that ye are my disciples, if ye shall have love one to another."
John 14:15
"If ye love me, keep my commandments,
Hebrews 13:1
Let brotherly love continue.