'Lye' in the Bible

“If I were to wash myself with snowAnd cleanse my hands with lye,

“And I will turn My hand against you,And will [thoroughly] purge away your dross as with lyeAnd remove all your tin (impurity).

“For though you wash yourself with lyeAnd use much soap,The stain of your guilt is [still] before Me [and you are soiled and dirty],” says the Lord God.