When the Holy One, blessed be He, created the world
Rabbi Shimon says that when the Holy One created the world He engraved on the upper and the lower worlds the letters of His Holy Name, which hold the secret of the supernal lights. The upper world is concealed in one of these letters; it ascends by means of the secret of infinity, and from this concealment emerges a thin and hidden light. In this light exists its counterpart, the glorious light of creation. When first it was struck, the supernal world emerged and was filled with a light so great that it would be too terrifying for those below to see. In this unknown concealed world live six thousand 'myriads' - which are supernal inhabitants and hosts and camps. Only Jacob, who possessed Malchut as his own, received permission to rise to the higher world. And, we learn, Malchut is illuminated by the light of Binah from above. The lower world always has a secret desire for the higher world, being unable to experience it directly as Jacob did.
The letters inscribed below connect us to letters of the Holy Name י.ה.ו.ה., which embody the primordial forces of Creation. This awesome luminosity is normally far too intense for a mortal to behold. However, through Jacob - who personifies control over physical existence - we have a key to unlock the gate to the upper world. Through Jacob, we acquire the vessel necessary to hold this divine energy that shines so brightly in the distant heavens.