A linen girdle - The appointed dress of the priestly order (Leviticus 16:4, ...).
Put it not in water - i. e., do not wash it, and so let it represent the deep-grained pollution of the people.
Related Commentaries of Jeremiah 13:1
Jeremiah 13:1
1 Thus saith the LORD unto me, Go and get thee a linen girdle, and put it upon thy loins, and put it not in water.