(1) In the days when the chieftains ruled, there was a famine in the land; and a man of Bethlehem in Judah, with his wife and two sons, went to reside in the country of Moab. (2) The man’s name was Elimelech, his wife’s name was Naomi, and his two sons were named Mahlon and Chilion—Ephrathites of Bethlehem in Judah. They came to the country of Moab and remained there. (3) Elimelech, Naomi’s husband, died; and she was left with her two sons. (4) They married Moabite women, one named Orpah and the other Ruth, and they lived there about ten years. (5) Then those two—Mahlon and Chilion—also died; so the woman was left without her two sons and without her husband. (6) She started out with her daughters-in-law to return from the country of Moab; for in the country of Moab she had heard that the LORD had taken note of His people and given them food.
Megillat Ruth begins with a reminder that marrying Moabite women is forbidden.
(א) וּכְכַלּ֣וֹת אֵ֗לֶּה נִגְּשׁ֨וּ אֵלַ֤י הַשָּׂרִים֙ לֵאמֹ֔ר לֹֽא־נִבְדְּל֞וּ הָעָ֤ם יִשְׂרָאֵל֙ וְהַכֹּהֲנִ֣ים וְהַלְוִיִּ֔ם מֵעַמֵּ֖י הָאֲרָצ֑וֹת ...(ב) כִּֽי־נָשְׂא֣וּ מִבְּנֹֽתֵיהֶ֗ם לָהֶם֙ וְלִבְנֵיהֶ֔ם וְהִתְעָֽרְבוּ֙ זֶ֣רַע הַקֹּ֔דֶשׁ בְּעַמֵּ֖י הָאֲרָצ֑וֹת... (ס)
(1) Now when these things were done, the princes drew near unto me, saying: ‘The people of Israel, and the priests and the Levites, have not separated themselves from the peoples of the lands....(2) For they have taken of their daughters for themselves and for their sons; so that the holy seed have mingled themselves with the peoples of the lands...
(א) וּכְהִתְפַּלֵּ֤ל עֶזְרָא֙ וּכְ֨הִתְוַדֹּת֔וֹ בֹּכֶה֙ וּמִתְנַפֵּ֔ל לִפְנֵ֖י בֵּ֣ית הָאֱלֹהִ֑ים נִקְבְּצוּ֩ אֵלָ֨יו מִיִּשְׂרָאֵ֜ל קָהָ֣ל רַב־מְאֹ֗ד אֲנָשִׁ֤ים וְנָשִׁים֙ וִֽילָדִ֔ים כִּֽי־בָכ֥וּ הָעָ֖ם הַרְבֵּה־בֶֽכֶה׃ (ס) (ב) וַיַּעַן֩ שְׁכַנְיָ֨ה בֶן־יְחִיאֵ֜ל מִבְּנֵ֤י עולם [עֵילָם֙] וַיֹּ֣אמֶר לְעֶזְרָ֔א אֲנַ֙חְנוּ֙ מָעַ֣לְנוּ בֵאלֹהֵ֔ינוּ וַנֹּ֛שֶׁב נָשִׁ֥ים נָכְרִיּ֖וֹת מֵעַמֵּ֣י הָאָ֑רֶץ וְעַתָּ֛ה יֵשׁ־מִקְוֶ֥ה לְיִשְׂרָאֵ֖ל עַל־זֹֽאת׃ (ג) וְעַתָּ֣ה נִֽכְרָת־בְּרִ֣ית לֵ֠אלֹהֵינוּ לְהוֹצִ֨יא כָל־נָשִׁ֜ים וְהַנּוֹלָ֤ד מֵהֶם֙ בַּעֲצַ֣ת אֲדֹנָ֔י וְהַחֲרֵדִ֖ים בְּמִצְוַ֣ת אֱלֹהֵ֑ינוּ וְכַתּוֹרָ֖ה יֵעָשֶֽׂה׃
(1) Now while Ezra prayed, and made confession, weeping and casting himself down before the house of God, there was gathered together unto him out of Israel a very great congregation of men and women and children; for the people wept very sore. (2) And Shecaniah the son of Jehiel, one of the sons of Elam, answered and said unto Ezra: ‘We have broken faith with our God, and have married foreign women of the peoples of the land; yet now there is hope for Israel concerning this thing. (3) Now therefore let us make a covenant with our God to put away all the wives, and such as are born of them, according to the counsel of the LORD, and of those that tremble at the commandment of our God; and let it be done according to the law.
והבועל ארמית, קנאין פוגעין בו.
And one who sleeps with an Aramean woman—zealots may attack him.
The rabbis resolve the problem by finding a conversion process for Ruth in the text. In Ruth Rabbah, a collection of midrash on Ruth, Ruth 1: 16-17 becomes Ruth's "Intro to Judaism" class. Naomi instructs Ruth as they walk across the Judean Desert from Moab to Bethlehem:
(16) And Ruth said: ‘Entreat me not to leave you, and to return from following after you; for where you go, I will go; and where you lodge, I will lodge; you people shall be my people, and your God my God; (17) where you die, will I die, and there will I be buried; the LORD do so to me,and more also, if anything but death part you and me.’
(כב) ותאמר רות אל תפגעי בי לעזבך לשוב מאחריך מהו אל תפגעי בי? אמרה לה: לא תחטא עלי, לא תסבין פגעיך מני לעזבך לשוב מאחריך. מכל מקום דעתי להתגייר. אלא מוטב על ידך ולא על ידי אחרת. כיון ששמעה נעמי כך, התחילה סודרת לה הלכות גרים. אמרה לה: בתי אין דרכן של בנות ישראל לילך לבתי תיאטראות ולבתי קרקסיאות שלהם. אמרה לה: אל אשר תלכי אלך. אמרה לה: בתי אין דרכן של ישראל לדור בבית שאין שם מזוזה. אמרה לה: באשר תליני אלין. עמך עמי אלו עונשין ואזהרות. ואלהיך אלהי שאר מצות.
(22) "And Ruth said, 'Do not urge me to leave you, to turn and not follow after you'(Ruth 1:16)." What does it mean, 'do not urge me'? She said to her, "Do not sin against me, do not turn your misfortunes from me." "To turn and follow after you(ibid)." It has been my intention in every instance to convert, but it is better at your hands than at the hands of another. When Naomi heard this she began to expound to her the laws of converts. She said to her, "My daughter, it is not the custom of daughters of Israel to go to their theaters and their circuses. She replied to her, "Where you go, I will go (ibid." She said to her, "My daughter, it is not the custom of Israel to dwell in a house that does not have a mezuzah." She replied to her, "Where you lodge I will lodge.(ibid)." "Your people will be my people (ibid)," these are the punishments and the warnings. "And Your God will be my God (ibid)," the other commandments.