2 Timothy 4:15
You should beware of him, for he strongly opposed our message.
Matthew 10:16-17
Here is how it will be: I am sending you out like sheep among wolves; therefore you should be as crafty [Note: The Greek word here is "sensible"] as snakes, yet as harmless [Note: The Greek word is "sincere"] as doves.
Philippians 3:2
Watch out for the "dogs!" [Note: "Dogs" were viewed with disgust by the ancient Jews (Deut. 23:18; II Kings 8:13; Rev. 22:15), so the term is used here derogatorily for Jewish Christians who were trying to impose on the church the requirements of the law of Moses]. Watch out for the evil workers! Watch out for those who mutilate the body meaninglessly! [Note: Paul here alludes, in a derogatory wordplay, to the Jewish practice of circumcision].
2 Timothy 3:8
These people oppose the truth just like Jannes and Jambres opposed Moses. They have corrupt minds and are worthless as far as the faith is concerned.