Contradiction with Exodus 14:14
Joshua 6:7 instructs active marching, while Exodus 14:14 emphasizes remaining still and letting the Lord fight.
Exodus 14:14: The LORD shall fight for you, and ye shall hold your peace.
Contradiction with Matthew 5:9
Joshua 6:7 involves warlike action, whereas Matthew 5:9 blesses peacemakers.
Matthew 5:9: Blessed [are] the peacemakers: for they shall be called the children of God.
Contradiction with Romans 12:19
Joshua 6:7 conveys taking action in battle, while Romans 12:19 advises against taking vengeance but leaving it to God.
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 James 3:18
Joshua 6:7 implies preparation for conflict, whereas James 3:18 speaks of peace made by those who sow in peace.
James 3:18: And the fruit of righteousness is sown in peace of them that make peace.
Contradiction with Proverbs 25:21-22
Joshua 6:7 involves military action, while Proverbs 25:21-22 advises showing kindness to enemies.
Proverbs 25:21-22: If thine enemy be hungry, give him bread to eat; and if he be thirsty, give him water to drink: