Deuteronomy 23:3

3An Ammonite or 23:3 Ruth, one of the ancestors of Jesus, was a Moabitess, but she essentially became an Israelite (Ruth 1:16) and married an Israelite (Boaz). Moreover, the rabbis taught that Deut 23:3 applied only to Ammonite and Moabite men. This teaching was summarized by what became a common saying: “An Ammonite [is forbidden], but not an Ammonitess; a Moabite, but not a Moabitess!” (as quoted from the Talmud).Moabite shall not enter the assembly of the Lord; none of their descendants, even to the tenth generation, shall ever enter the assembly of the Lord,