Ruth shows her godliness and obeys everything her mother-in-law told her to do.
The place where Ruth goes is the threshing floor, this is where all the harvested grain is kept, and men often slept near the grain so robbers wouldn’t break in and steal their crops. The threshing floor was not a very clean or nice place to be. It was a common place for prostitution in Israel, because the men often had large amounts of money in their pockets from the grain they’ve sold, but Boaz can’t leave his grain or someone will run off with it, so there he is, and here comes Ruth.
She uncovers Boaz’s feet and lays down. 3:8 says that about midnight Boaz woke up, probably because he was cold and felt a draft from being uncovered. What is he going to say? Everything is now hanging on how Boaz responds to this! He turns over, notices someone lying next to him, and says “Who are you?” Boaz didn’t say this because he was still drunk from before; he was a godly man who knew drunkenness was offensive to God. He said this because it was dark. Ruth answers in 3:9 and asks Boaz to propose to her. Really? Yep. Putting your blanket over a woman in their day was the same as putting a ring on a woman’s finger in our day.
Ruth is being very bold here by asking this, a woman asking a man, a Moabite asking an Israelite, an employee asking her employer, a young woman asking an older man! She’s basically saying, “Love me, protect me, hold me close, ask me to marry you.” By asking Boaz to, spread his covering (or “wing” in the original Hebrew) she is asking Boaz to be like God and “cover her with his wing.” This reminds of Boaz’s prayer in 2:12. She’s asking Boaz to answer this prayer in a deeper way now. She’s asking Boaz to ask her to be his wife. She’s saying “I would love to be your wife. Make your move Boaz.”
Notice Boaz though. Will he take advantage of her? No one would know right? Even if Ruth told someone what he did no one would believe the word of a Moabite over the word of an Israelite. Will Boaz think she’s trying to take advantage of him and ruin his own reputation? Boaz is a holy man, he could have her stoned, and killed, and than Naomi would have nothing left. This scene is just loaded and ripe with sexual tension, and people say the Bible is boring.
But look at what Boaz does: he wakes up, turns over, asks who’s there, hears what Ruth is proposing and says, “May you be blessed of the Lord my daughter!” Yes! He stops the situation from escalating any higher than it already is! This is a godly man! This is a man who doesn’t fit in with today’s modern ideas about sex and marriage! Oh how I want us to be like Boaz here. Rather than giving in to what we all know he wanted, he stops it and directs the conversation Godward.