“to your mother-in-law.” Boaz was concerned for Naomi, and exemplified the heart of the Law (Deut. 24:17-21).
“Do not go empty-handed to your mother-in-law.” This is the second time the word “empty” occurs in Ruth, the first being Ruth 1:21, when Naomi said that she had left Bethlehem full, but that Yahweh had brought her back “empty.” It surely seems that Naomi’s situation is changing, and she is getting filled by people who love Yahweh.
These are the last words spoken by Ruth in the Book of Ruth, and they show the same heart that Ruth has shown ever since she first came on the scene in chapter one; her concern for others and especially Naomi. Surely this conversation between Ruth and Naomi was long and emotional, and the Author could have chosen many different statements to be Ruth’s last words. The fact that He chose them to be about Boaz taking care of Naomi is no accident, then the scene quickly changes to Ruth 4.
Ruth 4 is dominated by Boaz negotiating to be the kinsman-redeemer, comfort to Naomi, and the royal genealogy of King David. We know that Boaz married Ruth and that Ruth had the baby Obed, but more about Ruth than that is only speculation. Also, Boaz was much older than Ruth, he likely being at least 90 and her being in her mid-twenties when they married, so we can only guess at what might have happened to Ruth after Boaz died.
If the Book of Ruth occurred during the judgeship of Deborah as the genealogy in Ruth 4 suggests, Ruth would have been alive and Boaz likely dead when the Israelites rejected Yahweh again and were subsequently afflicted by the Midianites and Amalekites during the time of Gideon. At that time the Midianites and Amalekites, who came from the south and east but likely entered Israel north of the Dead Sea, “encamped against them [Israel] and destroyed the produce of the land as far as Gaza, and left no sustenance in Israel, and no sheep or ox or donkey” (Judg. 6:4). Gaza is southwest of Bethlehem, and so while it is possible that the Midianites bypassed the central hill country of Israel and came down from the north through the Shephelah and coastal plain, it is quite possible that they went right through the breadbasket of southern Israel and thus would have devastated Bethlehem in their attacks. In any case, the Midianites and Amalekites so afflicted Israel that “Israel was brought very low because of Midian” (Judges 6:6), so it could not have been a good time for Ruth, who would likely have been still alive but likely in her late 40s or older.