 Chapter 3 of tractate Ketubot in the Mishnah, Tosefta, and Babylonian Talmud interpreted the laws of seducers and rapists in 

Interpreting “An Ammonite or a Moabite shall not enter into the assembly of the Lord,” the Mishnah taught that whereas an Ammonite and a Moabite are forbidden to enter into the congregation of Israel, their women are permitted immediately (following conversion).The Babylonian Talmud reported that Rava said that this tradition came from the prophet Samuel, and it thus allowed David (whom reports descended from Ruth the Moabite) and his family to marry into the Israelite congregation.Rabbi Abba bar Kahana said that all of Balaam's curses, which God turned into blessings, reverted to curses (and Balaam's intention was eventually fulfilled), except for Balaam's blessing of Israel's synagogues and schoolhouses, for says, "But the Lord your God turned the "curse" into a blessing for you, because the Lord your God loved you," using the singlular "curse," and not the plural "curses" (so that God turned only the first intended curse permanently into a blessing, that concerning synagogues and school-houses, which are destined never to disappear from Israel).