What does Ruth 3:12 mean?

Naomi returned to Bethlehem from Moab after the deaths of her husband and sons; her Moabite daughter-in-law, Ruth, insisted on accompanying her (Ruth 1). Ruth has spent the last two months gleaning from the fields of Boaz (Ruth 2:23). Naomi mentioned in passing that Boaz is a "redeemer"—he is a relative of Elimelech, Naomi's late husband, so he has the responsibility of buying Elimelech's land from the man he sold it to when they went to Moab (Leviticus 25:25–28, 47–49; Ruth 2:20). But Boaz mentions that Elimelech has a nearer relative who has the first right of refusal.

As the harvest was finishing up, Naomi told Ruth to take off her widow's clothes and present herself to Boaz as a potential wife (Ruth 3:3). Naomi knows Bethlehem well—she must know about this other redeemer. So why did Naomi send Ruth to Boaz? Because Naomi's priority is that Ruth find a good husband where she can find rest (Ruth 3:1)—this has always been her priority (Ruth 1:9). Kinsmen-redeemers have nothing to do with marriage, only land.

It doesn't occur to Naomi to arrange for a levirate marriage (Deuteronomy 25:5–6). Boaz is not the brother of Elimelech or Elimelech's son, and apparently neither is this other redeemer. They aren't obliged under the law to provide Elimelech with an heir. It's Ruth who decides Naomi needs an heir and Boaz is close enough. She combines the responsibilities of kinsman-redeemer and levirate brother. Boaz is so impressed with Ruth's willingness to do whatever it takes to restore Naomi's honor that he agrees.

The problem is this other kinsman. In fact, his existence may be why Boaz didn't offer to buy Elimelech's land when Naomi first arrived. Undoubtedly, Ruth would gratefully marry Boaz because of who he is, but Boaz knows he's not her first priority. He promises to do what it takes to fulfill her wishes: find a man to buy the land and give her a son.