Wolf in Sheeps Clothing

A wolf in sheep’s clothing is someone who appears to be friendly and to be concerned with your best interest, but who actually has hidden motives to take advantage of you or use you in some manner. 

The idiom wolf in sheep’s clothing is found in the New Testament, “Matthew 7:15” – “Beware of false prophets, which come to you in sheep’s clothing, but inwardly they are ravening wolves.”