"The Talmud states: 'The deeds of the righteous are greater than the making of the heavens and the earth.' The explanation of this is that the creation of the heavens and the earth was the formation of the reality of something from nothing. By contrast the righteous transform reality back to nothingness. For from all the things they do, even physical things like eating, they raise the holy sparks [tikkun] from this food upward, and the same is true of every matter they engage in. So we find that they transform the real into the divine Nothing."
-Rabbi Dov Ber of Mezeritch (from 'Maggid Devarav LeYaakov)