Luke 3:7 He said therefore to the crowds that came out to be baptized by him, “You brood of vipers! Who warned you to flee from the wrath to come?
Jeremiah 36:3 It may be that the house of Judah will hear all the disaster that I intend to do to them, so that every one may turn from his evil way, and that I may forgive their iniquity and their sin.”
John the Baptist is an OT prophet and may well be warning the Pharisees and Scribes of the coming destruction of Judah and the Temple (because of their denial of the promised Messiah).
We can read many similar warnings pertaining to salvation from the coming wrath of God upon a wicked world that also rejects Jesus as God and Saviour -
John 3:36 Whoever believes in the Son has eternal life; whoever does not obey the Son shall not see life, but the wrath of God remains on him.
Romans 5:9 Since, therefore, we have now been justified by his blood, much more shall we be saved by him from the wrath of God.
10 For if while we were enemies we were reconciled to God by the death of his Son, much more, now that we are reconciled, shall we be saved by his life.
Ephesians 5:6 Let no one deceive you with empty words, for because of these things the wrath of God comes upon the sons of disobedience.
Colossians 3:5 Put to death therefore what is earthly in you: sexual immorality, impurity, passion, evil desire, and covetousness, which is idolatry.
6 On account of these the wrath of God is coming.
1Thessalonians 1:9 For they themselves report concerning us the kind of reception we had among you, and how you turned to God from idols to serve the living and true God,
10 and to wait for his Son from heaven, whom he raised from the dead, Jesus who delivers us from the wrath to come.