He would not give the devil a knife to cut his throat.
More Italian Proverbs:
A small woman always seems newly married.Italian
He who is the cause of his own misfortune may bewail it himself.
Italian
The full cask makes no noise.
Italian
For an honest man half his wits are enough; the whole is too little for a knave.
Italian
To every saint his torch.
Italian
He's a friend at sneezing-time--the most that can be got from him is a "God bless you."
Italian