Fish and guests smell after three days. ~ English Proverb [16557]

Notable use:

"You are a guest in Philadelphia. Fish and guests stink after three days." ~ Benjamin Franklin to John Adams in the HBO mini-series "John Adams" based on the Pulitzer Prize winning book by David McCullough.

Alternate version:

Guests, like fish, begin to smell on the third day. ~ Jewish Proverb [16732]