§ Of the Return of the Noldor The Silmarillion

Then the brothers of Maedhros drew back, and fortified a great camp in Hithlum; but Morgoth held Maedhros as hostage, and sent word that he would not release him unless the Noldor would forsake their war, returning into the West, or else departing far from Beleriand into the South of the world. But the sons of Fëanor knew that Morgoth would betray them, and would not release Maedhros, whatsoever they might do; and they were constrained also by their oath, and might not for any cause forsake the war against their Enemy. Therefore Morgoth took Maedhros and hung him from the face of a precipice upon Thangorodrim, and he was caught to the rock by the wrist of his right hand in a band of steel.