Jeremiah 2:22 - Matthew Poole's English Annotations on the Holy Bible

Though interpreters do greatly vary. in describing what is particularly meant here by nitre and soap, and it would be superfluous to mention here; yet all agree they are some materials that artists make use of for the cleansing away spots from the skin, clothes, or other things; and the sense is plain, that the blot of his people is by no art to be taken out: it cannot be covered by excuses; Though thou wouldst dissemble thy idolatries, thou canst not deceive me: nor expiated by sacrifices; it is beyond the power of all superstitious or religious washings to cleanse away, which may be understood by these natural and artificial ways of cleansing. Thine iniquity is marked: the meaning seems to be either, Thy filthiness is so foul that it leaves a brand behind it that cannot be hid or washed out, but will abide: see Jeremiah 17:1. Or, according to another acceptation of the word, it is laid up with God. See the like Deuteronomy 32:34 Hosea 13:12. Purge thee, wash thee, do what thou wilt, thou canst by no means conceal thy wickedness from me, Job 9:20. They that would see greater variety of interpretations, let them consult the Synopsis.