Have you not considered those who were forbidden from private conversation [i.e., ridicule and conspiracy] and then return to that which they were forbidden and converse among themselves about sin and aggression and disobedience to the Messenger? And when they come to you, they greet you with that [word] by which Allāh does not greet you and say among themselves, "Why does Allāh not punish us for what we say?" Sufficient for them is Hell, which they will [enter to] burn, and wretched is the destination.

Sahih International