§ Of the Ruin of Doriath The Silmarillion

Now word went swiftly among the Elves of Ossiriand that a great host of Dwarves bearing gear of war had come down out of the mountains and passed over Gelion at the Ford of Stones. These tidings came soon to Beren and Lúthien; and in that time also a messenger came to them out of Doriath telling of what had befallen there. Then Beren arose and left Tol Galen, and summoning to him Dior his son they went north to the River Ascar; and with them went many of the Green-elves of Ossiriand.