a wolf in sheep's clothing

a wolf in sheep's clothing批着羊皮的狼；貌善心恶的人
耶稣在加利利一带传道布教，收了很多信徒 。有一天，他对门徒说:"Beware of false prophets,which come to you in sheep's clothing,but inwardly they are ravening wolves""
eg:Mrs.Martin trusted the lawyer until she realized that he was a wolf in sheep's clothing