Contradiction with Exodus 20:13
"Thou shalt not kill" contradicts the actions in Numbers 31:13, where the aftermath of a battle results in the killing of captives.
Exodus 20:13: Thou shalt not kill.
Contradiction with Matthew 5:44
"Love your enemies" contradicts the engagement in battle and treatment of captives implied in Numbers 31:13.
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 Proverbs 24:17
"Rejoice not when thine enemy falleth" contradicts the victorious return and implied actions of Numbers 31:13.
Proverbs 24:17: Rejoice not when thine enemy falleth, and let not thine heart be glad when he stumbleth:
Contradiction with Romans 12:19
"Avenge not yourselves" contradicts the vengeful nature of the campaign in Numbers 31:13.
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 Isaiah 2:4
"They shall beat their swords into plowshares" contradicts the continuation of warlike actions as described in Numbers 31:13.
Isaiah 2:4: And he shall judge among the nations, and shall rebuke many people: and they shall beat their swords into plowshares, and their spears into pruninghooks: nation shall not lift up sword against nation, neither shall they learn war any more. [pruninghooks: or, scythes]
Contradiction with Matthew 26:52
"For all they that take the sword shall perish with the sword" contradicts the militaristic actions following the battle in Numbers 31:13.
Matthew 26:52: Thinkest thou that I cannot now pray to my Father, and he shall presently give me more than twelve legions of angels?
Contradiction with James 2:13
"For he shall have judgment without mercy" contradicts any lack of mercy in the handling of captives as seen in Numbers 31:13.
James 2:13: For he shall have judgment without mercy, that hath shewed no mercy; and mercy rejoiceth against judgment. [rejoiceth: or, glorieth]