Maritime Provençal
Despènde lou pendu e lou pendu te pendra tu.
Meaning
Cut down the hanged man and the hanged man will hang you.
Note : Before doing someone a favour, make sure he deserves it.
Theme
Source : La Tour-Keyrié, Recueil de proverbes provençaux (1882), Gallica — public domain. Maritime Mistralian normalisation by Lingua Nostra.