§ Of the Beginning of Days The Silmarillion

Now it came to pass that while the Valar rested from their labours, and watched the growth and unfolding of the things that they had devised and begun, Manwë ordained a great feast; and the Valar and an their host came at his bidding. But Aulë and Tulkas were weary; for the craft of Aulë and the strength of Tulkas had been at the service of an without ceasing fax the days of their labour. And Melkor knew of an that was done, for even then he had secret friends and spies among the Maiar whom he had converted to his cause; and far off in the darkness he was filled with hatred, being jealous of the work of his peers, whom he desired to make subject to himself. Therefore he gathered to himself spirits out of the halls of Eä that he had perverted to his service, and he deemed himself strong. And seeing now his time he drew near again to Arda, and looked down upon it, and the beauty of the Earth in its Spring filled him the more with hate.