Midrash sur Ruth 1:4

“They took for themselves Moavite wives: the name of one was Orpa, and the name of the second was Ruth; and they dwelled there approximately ten years” (Ruth 1:4).
“They took for themselves Moavite wives.” It is taught in the name of Rabbi Meir: They did not convert them, they did not immerse them, the halakha had not yet been innovated, such that they would not have been punished for them; an Ammonite and not a female Ammonite, a Moavite and not a female Moavite.⁸⁸It had not yet been clarified that the Torah’s prohibition against marrying a convert from the nations of Amon and Moav (see Deuteronomy 23:4) applied only to male converts and not to female converts (see Yevamot 76b-77a). Maḥlon and Kilyon married them despite the fact that they did not convert, and despite the fact that, as far as they were aware, it was forbidden to marry them even if they converted.
“The name of one was Orpa,” because she turned her back [oref] to her mother-in-law. “And the name of the second was Ruth [Rut],” because she saw [ra’ata] truth in the words of her mother-in-law. Rabbi Beivai said in the name of Rabbi Reuven: Ruth and Orpa were the daughters of Eglon, as it is stated: “I have a secret matter for you king.⁸⁹Eglon, king of Moav. He said: Be silent…” (Judges 3:19), and it is written: “Ehud came to him…Ehud said: I have a matter of God to you, and he stood from his throne” (Judges 3:20). The Holy One blessed be He said to him: ‘You arose from your throne in deference to Me, by your life, I will establish a son from you who will sit on the throne of God.’
“They dwelled there approximately ten years.” [Whenever a verse uses this terminology, such as:]“Approximately thirty” (Judges 20:31), “approximately forty” (Joshua 4:13), [it means a bit] less or more [than the stated number].