וְאָשִׁ֤יבָה יָדִי֙ עָלַ֔יִךְ וְאֶצְרֹ֥ף כַּבֹּ֖ר סִיגָ֑יִךְ וְאָסִ֖ירָה כָּל־בְּדִילָֽיִךְ׃
And I will turn My hand upon thee, And purge away thy dross as with lye, And will take away all thine alloy;
Rashi on Isaiah
And I will return My hand upon you One blow after another, until the transgressors have been completely destroyed.
Rashi on Isaiah
as with lye This is an expression meaning soap [sbon in O.F., savon (in modern French)]. Its deviation is an expression of cleanliness, similar to (Ps. 24:4): “and pure (בַּר) of heart,” since it cleanses the garment of its stains.