§ Of the Voyage of Eärendil and the War of Wrath The Silmarillion

But Maedhros answered that if they returned to Aman but the favour of the Valar were withheld from them, then their oath would still remain, but its fulfilment be beyond all hope; and he said: 'Who can tell to what dreadful doom we shall come, if we disobey the Powers in their own land, or purpose ever to bring war again into their holy realm?'