'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?

Behold, I send you forth as sheep in the midst of wolves: be ye therefore wise as serpents, and harmless 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.

Ye serpents, ye generation of vipers, how can ye escape the damnation of hell?