“wash yourself, anoint yourself, put on your nice garment.” Ruth was going to propose that Boaz marry her, and so she made herself presentable for that occasion. It is questionable how much of Ruth’s somewhat elaborate preparations were recognized by Boaz, given the fact that Ruth approached Boaz in the dark. But if Boaz noticed even some of them, many years of living in that culture would have immediately and instinctively indicated to him that this was the behavior of a bride, and that alone would have made it quite obvious to him why Ruth was there at his feet and what she wanted, which soon she would explicitly ask for. There is no indication, however, that Ruth was in any way trying to seduce Boaz at this time (although some people have suggested that) and no indication on Boaz’s part that he would have agreed to such an encounter anyway. Frankly, given Boaz’s noble character, and given the history of Israel and the fact that during their wilderness wanderings the Moabite women used ritual sex to seduce the men of Israel to worship pagan gods (Num. 25:1-9), any hint that Ruth the Moabitess was trying to seduce Boaz would have almost certainly repulsed him and soured his relationship with both Ruth and Naomi (see commentary on Ruth 3:4, “uncover his feet”).
“go down to the threshing floor.” The grazing land to the east of Bethlehem was a little lower in elevation than the town of Bethlehem, so people had to “go down” to the threshing floor. Then people go “up” into the city (Ruth 4:1).
“until he has finished eating and drinking.” It was very common that at mealtime the men of a clan ate together and then later the women and children. Naomi’s advice that Boaz finish eating and drinking was not only so he would be relaxed, but also so Ruth, who was already being somewhat aggressive in asking for Boaz to marry her, would not appear desperate, and furthermore, she had to meet him alone, when he was away from all the other men.