He knows where the devil carries his tail.
More Italian Proverbs:
Hard upon hard never made a good wall.Italian
Whoever brings finds the door open for him.
Italian
Let us first catch the bear and then sell its skin.
Italian
Vetches seem bitter to the full-cropped pigeon.
Italian
Look with suspicion on the flight of an enemy.
Italian
If you let them put the calf on your shoulders, it will not be long before they clap on the cow.
Italian