Matthew 3:7-8 But when he saw many of the Pharisees and Sadducees coming to his baptism, he said to them, "Brood of vipers! Who warned you to flee from the wrath to come? Therefore bear fruits worthy of repentance,...
There's such a thing as telling a person that if he repeats a prayer he'll be saved, and then the person believes it. But that isn't what happened here. The Pharisees and Sadducees knew that they had rejected John's message of repentance, but they wanted to be associated with him anyway. We don't know if their motives were honor, seizing control of the movement, or something else, but we know that their motive wasn't Godliness.
A viper is a person who knowingly pretends to be part of Christianity.
No fear of Divine wrath, no fruit of repentance