This Bible contradiction is from the Skeptic's Annotated Bible.
Deuteronomy 23:3 View context
An Ammonite or Moabite shall not enter into the congregation of the LORD; even to their tenth generation shall they not enter into the congregation of the LORD for ever:
Nehemiah 13:1 View context
On that day they read in the book of Moses in the audience of the people; and therein was found written, that the Ammonite and the Moabite should not come into the congregation of God for ever;
Ruth 1:4 View context
And they took them wives of the women of Moab; the name of the one [was] Orpah, and the name of the other Ruth: and they dwelled there about ten years.
Ruth 4:13 View context
So Boaz took Ruth, and she was his wife: and when he went in unto her, the LORD gave her conception, and she bare a son.