'Beware' in the Bible

"Beware of false prophets, who come to you in sheep's clothing, but inwardly are ravening wolves.

But beware of men: for they will deliver you up to councils, and in their synagogues they will scourge you.

Jesus said to them, "Take heed and beware of the yeast of the Pharisees and Sadducees."

How is it that you don't perceive that I didn't speak to you concerning bread? But beware of the yeast of the Pharisees and Sadducees."

Then they understood that he didn't tell them to beware of the yeast of bread, but of the teaching of the Pharisees and Sadducees.