Narrated by Anas bin Malik (Radi-Allahu 'anhu):

The Prophet (Sallallahu 'Alaihi Wa Sallam) was not one who would abuse (others) or say obscene words, or curse (others), and if he wanted to admonish anyone of us, he used to say: "What is wrong with him, his forehead be dusted!"

Bukhari Vol. 8 : No. 58