Psalm 58:4

They sharpen their tongues as a serpent; Poison of an asp is under their lips. Selah.

If the serpent bites before being charmed, there is no advantage for the charmer.

“For behold, I am sending serpents against you, Vipers, for which there is no charm, And they will bite you,” declares Yahweh.

“Thus says Yahweh of hosts, the God of Israel, ‘Behold, I am about to bring on this city and all its towns the entire calamity that I have spoken against it because they have stiffened their necks so as not to hear My words.’”

“But they refused to give heed and turned a stubborn shoulder and dulled their ears from hearing.