Deuteronomy 23:6
Thou shalt not seek their peace nor their prosperity all thy days for ever.
More from Deuteronomy 23
He that is wounded in the stones, or hath his privy member cut off, shall not enter into the congregation of the LORD.
A bastard shall not enter into the congregation of the LORD; even to his tenth generation shall he not enter into the congregation of the LORD.
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:
Because they met you not with bread and with water in the way, when ye came forth out of Egypt; and because they hired against thee Balaam the son of Beor of Pethor of Mesopotamia, to curse
Nevertheless the LORD thy God would not hearken unto Balaam; but the LORD thy God turned the curse into a blessing unto thee, because the LORD thy God loved