§ Of Fëanor and the Unchaining of Melkor The Silmarillion

Now even while Fëanor and the craftsmen of the Noldor worked with delight, foreseeing no end to their labours, and while the sons of Indis grew to their full stature, the Noontide of Valinor was drawing to its close. For it came to pass that Melkor, as the Valar had decreed, completed the term of his bondage, dwelling for three ages in the duress of Mandos, alone. At length, as Manwë had promised, he was brought again before the thrones of the Valar. Then he looked upon their glory and their bliss, and envy was in his heart; he looked upon the Children of Ilúvatar that sat at the feet of the Mighty, and hatred filled him; he looked upon the wealth of bright gems, and he lusted for them; but he hid his thoughts, and postponed his vengeance.