To spare and preserve means to take under our care, to look after the fourfold in its essence. What we take under our care must be kept safe. Mortals would never be capable of it if dwelling were merely a staying on earth under the sky, before the divinities, among mortals. Rather, dwelling itself is always a staying with things. Staying with things, however, is not merely something attached to this fourfold preservation as a fifth something.
Dwelling preserves the fourfold by bringing the essence of the fourfold into things.
But things themselves secure the fourfold only when they themselves as things are let be in their essence. In this way, that mortals nurse and nurture the things that grow, and specially construct things that do not grow. Cultivating and construction are building in the narrower sense. Dwelling, inasmuch as it keeps the fourfold in things, is, as this keeping, a building.