"What they say will spread like an infectious disease." Just as gangrene quickly spreads in a person's body and destroys it, what those people were saying would spread from person to person and harm the faith of those who heard it. Alternate translation: "Their word will spread quickly and cause destruction like gangrene" or "People will quickly hear what they say and be harmed by it." (See: [[rc://en/ta/man/translate/figs-simile]])
dead, rotting flesh. The only way to keep gangrene from spreading and killing the ill person is to cut off the affected area.
## wandered from the truth ##
This can mean 1) "have made errors about the truth" or "are in error about the truth," like an arrow missing its target, or 2) "have stopped believing in the truth."
## the resurrection has already happened ##
"God has already raised dead believers to eternal life"
## upsetting the faith of some ##
"making some believers doubt" or "convincing some believers to stop believing"