'Soap' in the Bible

If I have washed myself with snow-water, And purified with soap my hands,

But though thou dost wash with nitre, And dost multiply to thyself soap, Marked is thine iniquity before Me, An affirmation of the Lord Jehovah.

And who is bearing the day of his coming? And who is standing in his appearing? For he is as fire of a refiner, And as soap of a fuller.