פּירוש אויף רות 3:9

Spread your mantle. The corner of your garment to cover me with your cloak; and this is an expression of marriage.⁹An expression taken from birds who spread their wings [כנף] when they mate. (Malbim)

"ופרשת (and you shall spread):" A hint to take her as a wife.

For you are a near kinsman. To redeem my husband’s inheritance, as it is stated, “and a close relative comes and redeems, etc.”¹⁰Vayikra 25:25. And my mother-in-law and I must sell our inheritance, and now it is incumbent upon you to buy it. Acquire [i.e., marry] me also, along with it,¹¹The Torah requires only that he redeem the relative’s property, but it does not require that he redeem his relative’s wife. She therefore asked him to marry her. so that the name of the deceased be remembered upon his estate, so that when I come to the field they will say, “this is Machlon’s wife.”