Charles Ellicott Commentary Deuteronomy 23:3

"An Ammonite or a Moabite shall not enter into the assembly of Jehovah; even to the tenth generation shall none belonging to them enter into the assembly of Jehovah for ever:" — Deuteronomy 23:3 (ASV)

An Ammonite or Moabite shall not enter. According to Rashi, “shall not marry an Israelite woman.” It must be remembered that the children, according to Jewish law, follow the father, not the mother. The case of Ruth would not, therefore, be touched by this precept.