Dirty water does not wash clean.
More Italian Proverbs:
A good horse never lacks a saddle.Italian
The fox advised the others to cut off their tails, because he had left his own in the trap.
Italian
Evening red and morning grey help the traveler on his way; evening grey and morning red bring down rain upon his head.
Italian
The sun loses nothing by shining into a puddle.
Italian
Who changes country changes luck.
Italian
Many a true word in spoken in jest.
Italian