ייִדישער מחשבֿה אויף רות 1:16

And there is another general principle regarding forbidden sexual relationships: some prohibitions are based on the concept of species, while others are not limited to specific species. For example, in human beings and animals, there are prohibitions against same-sex relations, as stated in Genesis 8:1: "And God remembered Noah and all the beasts and all the cattle that were with him in the ark." This includes the honor that they were created together in one day. Similarly, in Exodus 21:33, it is mentioned that if a bull or a donkey falls into a pit, there is a greater consequence. The same principle applies to horses, oxen, and camels. Furthermore, there are prohibitions regarding a female that are not based on species, such as the prohibition against a man's mother, sister, or daughter. There are also prohibitions regarding relations with another man's wife, performing levirate marriage with a woman, or marrying a woman and her sister. There is also a prohibition against having relations with a woman who is not married according to Jewish law, as she has severed her connection to her people and her God. Ruth expressed this sentiment in Ruth 1:16, saying, "Your people shall be my people, and your God my God." If she engages in relations while not in a state of sanctity, she desecrates herself and her God. There is also a prohibition against treating one's wife as a virgin or a widow and against relations with one's wife during her menstrual and postpartum period, which results in impurity for both male and female.

The formula for conversion in the Book of Ruth contains these ‎two aspects, and their essence lies ‎in the four final words of Ruth to Naomi: “Your people shall be ‎my people, and your God my ‎God” (Ruth 1:16, emphasis added).‎

Simple, that is Ruth—what does she say?
“Wherever you go I will go and wherever you lodge I will lodge; your people is my people; your God is my God.” (Ruth 1:16)
We, too, were strengthened by her clinging to those her soul loves, and we will say to her: “May God make the woman who comes into your house like Rachel and like Leah, both of whom built built the House of Israel!” (Ruth 4:11)