§ Of the Sun and Moon and the Hiding of Valinor The Silmarillion

These things the Valar did, recalling in their twilight the darkness of the lands of Arda; and they resolved now to illumine Middle-earth and with light to hinder the deeds of Melkor. For they remembered the Avari that remained by the waters of their awakening, and they did not utterly forsake the Noldor in exile; and Manwë knew also that the hour of the coming of Men was drawn nigh. And it is said indeed that, even as the Valar made war upon Melkor for the sake of the Quendi, so now for that time they forbore for the sake of the Hildor, the Aftercomers, the younger Children of Ilúvatar. For so grievous had been the hurts of Middle-earth in the war upon Utumno that the Valar feared lest even worse should now befall; whereas the Hildor should be mortal, and weaker than the Quendi to withstand fear and tumult. Moreover it was not revealed to Manwë where the beginning of Men should be, north, south, or east. Therefore the Valar sent forth light, but made strong the land of their dwelling.