זוהר שמות — דף רט ע”א

The supernal spirit that descends upon a person in joy rejoices his soul, standing like the World to Come from which he will benefit. Just as a person delights this spirit in this world, that spirit delights him in the World to Come. Everything a person does for Heaven's sake returns to rejoice him afterward. A person must cause his soul and spirit to rejoice on Shabbat, thereby aiding the supernal union. The reward of Shabbat joy is that the soul merits unity with the supernal holiness.