Since the nature and capacity of the Order of Hishtalshelus as it comes down into the creation of the World of Action (the physical world) is extremely limited; therefore, in order that abundant Light from the Infinite Light of Hashem should shine there, this needs to come specifically through the aspect of Yitzchok, who embodied the “Source of Severities,” the “Lamp of Darkness,” which is also called “the ‘Kav’ (line) of Measuring,” which measures out and limits the Light so that it come into the level of Wisdom and other attributes.
Through these “severities” of Yitzchok, an additional measure of Light and Revelation can also be drawn down even as far as the physical world of Action. This is the meaning of the blessing: “And He will give to you, Elokim (Hashem as manifest in severity), from the dew of heaven etc.,” meaning that the blessing will also come down into the limitations of this world.
