Q. Having translated the book of Ruth, I’m curious about the poetic lines that Ruth recites to Naomi when she makes her pledge in chapter 2. I’m wondering if you know where these words come from in Hebrew culture? Given the marriage themes in the book, I have wondered if they might have been part of the ancient Israelite marital vows or something similar. The poetry absolutely stands out there. Any insight on this?

“Ruth Declares her Loyalty to Naomi”
To respond to this second question of yours, you’re right, Ruth’s words to Naomi really do stand out as Hebrew poetry, in parallel couplets. It’s surprising that Bibles don’t format them this way:
Entreat me not to leave you
or to return from following you;
for where you go I will go,
and where you lodge I will lodge;
your people shall be my people,
and your God my God;
where you die I will die,
and there will I be buried.
After elegantly concluding her poem by varying the you-I progression with a solemn final statement, Ruth swears an oath that she asks God to enforce: “May the Lord do so to me and more also if even death parts me from you!”
I don’t think this language is actually taken from an ancient Israelite marriage ceremony. (The opposite is true: people have taken Ruth’s words and turned them into marriage vows.) Rather, it’s characteristic of Hebrew narrative that when someone has something crucial to say, on which the story line turns, they say it in poetry. In the ancient oral culture, this would make the saying memorable and repeatable (kind of like an advertizing slogan today).
For example, when Sheba son of Bikri foments a rebellion against David, he shouts in poetry:
We have no share in David,
no part in Jesse’s son!
Every man to his tent, Israel!
To give another example, David’s promise to Bathsheba about who will succeed him is also spoken in poetry, and it’s quoted several times at crucial points in the succession narrative:
Solomon your son shall reign after me,
he shall sit upon my throne in my stead.
Samuel speaks similarly in poetry when he announces God’s rejection of Saul as king and when he pronounces judgment on Agag. The Israelites proclaim their refusal of Rehoboam as their king in poetry as well.
Examples like these show that poetry was used for important pronouncements in Hebrew narrative, probably reflecting the actual customs of the culture. And we have to admit that among her many other qualities as a “woman of noble character,” Ruth was a fine poet.