A snake can change its skin but not its disposition.
More Persian Proverbs:
The lover who gives you her body but not her heart is generous with thornless roses.Persian
Flies will never leave the shop of a sweetmaker.
Persian
When the cat and the mouse agree, the grocer is ruined.
Persian
A tear at the right moment is better than a misplaced smile.
Persian
The halfwit spoke, and the brainless believed.
Persian
Treat your superior as a father, your equal as a brother, and your inferior as a son.
Persian