Albert Barnes Commentary Ruth 1:11-13

"And Naomi said, Turn again, my daughters: why will ye go with me? have I yet sons in my womb, that they may be your husbands? Turn again, my daughters, go your way; for I am too old to have a husband. If I should say, I have hope, if I should even have a husband to-night, and should also bear sons; would ye therefore tarry till they were grown? would ye therefore stay from having husbands? nay, my daughters, for it grieveth me much for your sakes, for the hand of Jehovah is gone forth against me." — Ruth 1:11-13 (ASV)

See marginal references and notes. The Levirate law probably existed among the Moabites, and in Israel extended beyond the brother in the strict sense, and applied to the nearest relations, since Boaz was only the kinsman of Elimelech (Ruth 3:12).