Our Sages greatly extolled the virtue of charity, declaring it equal to all the other mitzvot together. Throughout the Jerusalem Talmud, charity is called simply "The Mitzvah"... Because in all other mitzvot, only one faculty of the vital soul is invested in the action. In the case of charity, however, which one gives from the proceeds of the toil of his hands, all the energy of his vital soul is invested in the effort of his labor. Also, even one who does not earn his livelihood from his labors, nevertheless, since he could have purchased with this money his life's sustenance, he is actually giving his soul’s life to G d...
Rabbi Schneur Zalman of Liadi (Tanya ch. 37)
