Cleanliness is NOT Next to Godliness
by Chris MacDonald
I don’t know about you, but most of the places I’ve ever been (worked, lived) people are heartily encouraged to do the dishes.
But I guess dishwashing is not welcome everywhere. This sign is in a public bathroom in Lieber State Recreation Area near Cagles Mill (or Cataract) Lake in Southern Indiana. (My guess is that food waste clogs the bathroom sink drains, or that people doing dishes take up more than their fair share of sink time.)
p.s., Thanks to Abe Schwab for the photo.
Normative Signs: The Poetry of "Ought" 
A further thought: This is just the kind of sign — and policy — that warrants further explanation as to its point. I can imagine lots of people seeing the sign, but failing to understand the rationale behind it, and hence ignoring it.