§ Of Beren and Lúthien The Silmarillion

But Carcharoth looked upon that holy jewel and was not daunted, and the devouring spirit within him awoke to sudden fire; and gaping he took suddenly the hand within his jaws, and he bit it off at the wrist. Then swiftly all his inwards were filled with a flame of anguish, and the Silmaril seared his accursed flesh. Howling he led before them, and the walls of the valley of the Gate echoes with the clamour of his torment. So terrible did he become in his madness that all the creatures of Morgoth that abode in that valley, or were upon any of the roads that led thither, fled far away; for he slew all living things that stood in his path, and burst from the North with ruin upon the world. Of all the terrors that came ever into Beleriand ere Angband's fall the madness of Carcharoth was the most dreadful; for the power of the Silmaril was hidden within him.