I don't usually go for the King Jim Version, but in this case I thought I'd make an exception. There's a certain poetry…
This insult isn't aimed at a particular person, which is slightly disappointing—and really, you could make a-whole-nother blog of nasty things said about “the fool” in the book of Proverbs—but the ugliness of the comparison qualifies the proverb for this page.
Step 1: Substitute “a fool returneth to his” for “thou returnest to thy”.
Step 2: Let loose at thy neighbour.
Cred Where Cred is Due
Thanks to Paul for suggesting this one.