There used to be false prophets among God's people, just as you will have some false teachers in your group. They will secretly teach things that are wrong -- teachings that will cause people to be lost. They will even refuse to accept the Master, Jesus, who bought their freedom. So they will bring quick ruin on themselves.
Many will follow their evil ways and say evil things about the way of truth.
Those false teachers only want your money, so they will use you by telling you lies. Their judgment spoken against them long ago is still coming, and their ruin is certain.
When angels sinned, God did not let them go free without punishment. He sent them to hell and put them in caves of darkness where they are being held for judgment.
And God punished the world long ago when he brought a flood to the world that was full of people who were against him. But God saved Noah, who preached about being right with God, and seven other people with him.
And God also destroyed the evil cities of Sodom and Gomorrahn by burning them until they were ashes. He made those cities an example of what will happen to those who are against God.