Chazal have said: For three transgressions punishment is exacted of a man in this world, and he has no share in the world to come: idolatry, illicit relations, and blood-spilling — and lashon hara over and above all. Chazal have proved this from Scripture. And the Rishonim have explained that the reference is to those who are habituated to this sin [lashon hara] and who do not take it upon themselves to guard themselves against it, the thing having become "permitted" to them.