1 John 4:20

If any person say, I love God, yet hateth his brother, he is a liar; for he who loveth not his brother whom he hath seen, how can he love the 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 in him the truth is not.

1 John 2:9

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

1 John 3:17

But whosoever hath worldly abundance, and seeth his brother under necessity, and shutteth his bowels of compassion against 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 abideth in us, and his love is perfected in us.

1 John 2:11

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

1 Peter 1:8

whom though ye have not seen, ye love; on whom, though ye have not as yet gazed, yet believing, ye exult with joy unutterable and glorious:

1 John 1:6

If we say that we have communion with him, and walk in darkness, we lie, and practise 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 in him the truth is not.
1 John 3:17
But whosoever hath worldly abundance, and seeth his brother under necessity, and shutteth his bowels of compassion against 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 abideth in us, and his love is perfected in us.

General references

Matthew 22:40
On these two commandments, the whole law and the prophets depend.
Matthew 25:42
for I was hungry, and ye gave me nothing to eat: I was thirsty, and ye gave me nothing to 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, keep my commandments.
Hebrews 13:1
LET brotherly love continue.