Deuteronomy 23:1-4 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 thee.

It is not referring to salvation but to being allowed to enter into or work in the temple. It is interesting to note that David was the 10th or 11th generation since this time - and his great grandmother was Ruth, the Moabite.

I couldn't imagine not being able to worship in the temple if I was an OT believer - it would be like never being able to worship with believers in a local church today. Still saved - but growth would be hindered and would be starving for fellowship.