For though thou wash thee with nitre, and take thee much soap, yet thine iniquity is marked before me, saith the Lord GOD.
Nitre - not what is now so called, namely, salt-petre; but the natron of Egypt, a mineral alkali, an incrustation at the bottom of the lakes, after the summer heat has evaporated the water: used for washing (cf. remarks, Job 9:30; Proverbs 25:20.)
Soap - potash, the carbonate of which is obtained impure from burning different plants, especially the kali of Egypt and Arabia. Mixed with oil, it was used for washing. Marked - deeply ingrained, indelibly marked; the Hebrew х kaatam (H3799)] being equivalent to х kaatab (H3789)]. Others translate 'is treasured up,' from the Arabic. Maurer, from a Syriac root, is polluted.