'Beware' in the Bible

“Beware of the false prophets, [teachers] who come to you dressed as sheep [appearing gentle and innocent], but inwardly are ravenous wolves.

How is it that you fail to understand that I was not talking to you about bread? But beware of the leaven of the Pharisees and Sadducees.”

Then they understood that He did not tell them to beware of the leaven of bread, but of the [false] teaching of the Pharisees and Sadducees.

“See that you do not despise or think less of one of these little ones, for I say to you that their angels in heaven [are in the presence of and] continually look upon the face of My Father who is in heaven.