§ Of Beren and Lúthien The Silmarillion

Many other words he spoke, as potent as were long before in Tirion the words of his father that first inflamed the Noldor to rebellion. And after Celegorm Curufin spoke, more softly but with no less power, conjuring in the minds of the Elves a vision of war and the ruin of Nargothrond. So great a fear did he set in their hearts that never after until the time of Túrin would any Elf of that realm go into open battle; but with stealth and ambush, with wizardry and venomed dart, they pursued all strangers, forgetting the bonds of kinship. Thus they fell from the valour and freedom of the Elves of old, and their land was darkened.