Contradiction with Matthew 5:44
While 1 Samuel 17:27 discusses the reward for slaying Goliath, Matthew 5:44 teaches to love enemies and do good to those who hate you.
Matthew 5:44: But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you;
Contradiction with Romans 12:19
In 1 Samuel 17:27, there is an expectation of a reward for the slayer of Goliath, yet Romans 12:19 urges leaving vengeance to God rather than seeking personal triumph or revenge.
Romans 12:19: Dearly beloved, avenge not yourselves, but [rather] give place unto wrath: for it is written, Vengeance [is] mine; I will repay, saith the Lord.
Contradiction with Proverbs 25:21-22
1 Samuel 17:27 is about defeating an enemy with violence, whereas Proverbs 25:21-22 encourages feeding and giving drink to your enemy, suggesting kindness over combat.
Proverbs 25:21-22: If thine enemy be hungry, give him bread to eat; and if he be thirsty, give him water to drink:
Contradiction with Luke 6:35
1 Samuel 17:27 discusses material reward for defeating an enemy, while Luke 6:35 encourages love for enemies without expectation of reward, focusing on heavenly reward instead.
Luke 6:35: But love ye your enemies, and do good, and lend, hoping for nothing again; and your reward shall be great, and ye shall be the children of the Highest: for he is kind unto the unthankful and [to] the evil.
Contradiction with Exodus 20:13
While 1 Samuel 17:27 implies killing for reward, Exodus 20:13 commands "Thou shalt not kill," promoting the preservation of life instead.
Exodus 20:13: Thou shalt not kill.