Deuteronomy 23:3-8

3An 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: 4Because they met you not with bread and with water in the way, when ye came forth from Egypt; and because they hired against thee Balaam the son of Beor of Pethor of Mesopotamia, to curse thee. 5Nevertheless the LORD thy God would not hearken to Balaam; but the LORD thy God turned the curse into a blessing to thee, because the LORD thy God loved thee. 6Thou shalt not seek their peace nor their prosperity all thy days for ever.1 7Thou shalt not abhor an Edomite; for he is thy brother: thou shalt not abhor an Egyptian; because thou wast a stranger in his land. 8The children that are begotten by them shall enter into the congregation of the LORD in their third generation.