'Serpents' in the Bible

But when John saw many Pharisees and Sadducees coming to where he was baptizing, he told them, "You children of serpents! Who warned you to flee from the coming wrath?

"Pay attention, now! I am sending you out like sheep among wolves. So be as cunning as serpents and as innocent as doves.

You children of serpents! How can you say anything good when you are evil? The mouth speaks about what overflows from the heart.

You snakes, you children of serpents! How can you escape being condemned to hell?