זוהר שמות — דף קלה ע”ב

The secret of Shabbat is that the Shekhinah unites in the secret of one and separates from the Other Side. When Shabbat enters, all judgments are removed from her and she remains in the unity of holy light. The Friday evening prayer opens with the blessing of Shabbat, and it is forbidden to open with a verse of judgment such as Vehu Rahum. Barukh Hashem Hamevorakha is the spring of the well from the source of life that waters and blesses everything.