This Bible contradiction is from the Skeptic's Annotated Bible.
Do not fight against them or take their land.
Deuteronomy 2:9 View context
And the LORD said unto me, Distress not the Moabites, neither contend with them in battle: for I will not give thee of their land [for] a possession; because I have given Ar unto the children of Lot [for] a possession.
Kill them and take their land.
Judges 3:28-30 View context
And he said unto them, Follow after me: for the LORD hath delivered your enemies the Moabites into your hand. And they went down after him, and took the fords of Jordan toward Moab, and suffered not a man to pass over.
And they slew of Moab at that time about ten thousand men, all lusty, and all men of valour; and there escaped not a man.
So Moab was subdued that day under the hand of Israel. And the land had rest fourscore years.
Jeremiah 48:2 View context
[There shall be] no more praise of Moab: in Heshbon they have devised evil against it; come, and let us cut it off from [being] a nation. Also thou shalt be cut down, O Madmen; the sword shall pursue thee.