A. We do not truly love God if we don't love our fellow man:

1JOH 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, how can he love God whom he hath not seen?

TIT 3:3. For we ourselves also were sometimes foolish, disobedient, deceived, serving divers lusts and pleasures, living in malice and envy, hateful, and hating one another.

TIT 3:4. But after that the kindness and love of God our Saviour toward man appeared,

TIT 3:5. Not by works of righteousness which we have done, but according to his mercy he saved us, by the washing of regeneration, and renewing of the Holy Ghost;

JAM 3:9. Therewith bless we God, even the Father; and therewith curse we men, which are made after the similitude of God.

JAM 3:10. Out of the same mouth proceedeth blessing and cursing. My brethren, these things ought not so to be.

JAM 3:11. Doth a fountain send forth at the same place sweet water and bitter?

JAM 3:12. Can the fig tree, my brethren, bear olive berries? either a vine, figs? so can no fountain both yield salt water and fresh.

JAM 3:14. But if ye have bitter envying and strife in your hearts, glory not, and lie not against the truth.

1JOH 3:17. But whoso hath this world's good, and seeth his brother have need, and shutteth up his bowels of compassion from him, how dwelleth the love of God in him?

1JOH 4:21. And this commandment have we from him, That he who loveth God love his brother also.

MAT 5:23. Therefore if thou bring thy gift to the altar, and there rememberest that thy brother hath ought against thee;

MAT 5:24. Leave there thy gift before the altar, and go thy way; first be reconciled to thy brother, and then come and offer thy gift.

B. We are commanded not to be hateful:

LEV 19:17. Thou shalt not hate thy brother in thine heart: thou shalt in any wise rebuke thy neighbour, and not suffer sin upon him.

LEV 19:18. Thou shalt not avenge, nor bear any grudge against the children of thy people, but thou shalt love thy neighbour as thyself: I am the LORD.

C. When we don't love one another:

1JOH 2:9. He that saith he is in the light, and hateth his brother, is in darkness even until now.

1JOH 2:10. He that loveth his brother abideth in the light, and there is none occasion of stumbling in him.

1JOH 2:11. But he that hateth his brother is in darkness, and walketh in darkness, and knoweth not whither he goeth, because that darkness hath blinded his eyes.

1JOH 3:10. In this the children of God are manifest, and the children of the devil: whosoever doeth not righteousness is not of God, neither he that loveth not his brother.

1JOH 3:14. We know that we have passed from death unto life, because we love the brethren. He that loveth not his brother abideth in death.

1JOH 3:15. Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him.

1JOH 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, how can he love God whom he hath not seen?

1JOH 4:8. He that loveth not knoweth not God; for God is love.

D. The bad fruit of hatred:

GEN 37:4. And when his brethren saw that their father loved him more than all his brethren, they hated him, and could not speak peaceably unto him.

PRO 10:12. Hatred stirreth up strifes: but love covereth all sins.

1JOH 3:15. Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him.

GEN 4:3. And in process of time it came to pass, that Cain brought of the fruit of the ground an offering unto the LORD.

GEN 4:4. And Abel, he also brought of the firstlings of his flock and of the fat thereof. And the LORD had respect unto Abel and to his offering:

GEN 4:5. But unto Cain and to his offering he had not respect. And Cain was very wroth, and his countenance fell.

GEN 4:6. And the LORD said unto Cain, Why art thou wroth? and why is thy countenance fallen?

GEN 4:7. If thou doest well, shalt thou not be accepted? and if thou doest not well, sin lieth at the door. And unto thee shall be his desire, and thou shalt rule over him.

GEN 4:8. And Cain talked with Abel his brother: and it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him.

PRO 26:26. Whose hatred is covered by deceit, his wickedness shall be shewed before the whole congregation.