"And Jacob made an end of commanding his sons"
Rabbi Yehuda explains that Jacob "commanded" his sons to be attached to the Shechinah, referencing the cave where Adam is buried, a place near the Garden of Eden. We're told that four couples are buried there, the three Patriarchs, their wives, and Adam and Eve. The Zohar explains that four are required to make up a Holy Chariot. The Creator, however, linked King David to the three Patriarchs to form the chariot. So why, Rabbi Yehuda asks, does Adam rest in the cave with the three Patriarchs while King David is buried elsewhere?
We are then told that Adam was allotted 1000 years of life, but 70 of his years were transferred to King David to allow for his physical existence.
Therefore, both King David and Adam signify Malchut, which represents Female. The three Patriarchs embody Zeir Anpin, which is Male. Thus, Adam could be the fourth aspect, "substituting" for David, allowing the Upper Worlds [the Patriarchs] and the Lower World [David or Adam] to be united. It is then explained that the cave where King David is buried corresponds to the male energy of the Upper World, whereas King David embodies the female energy of Malchut. Hence, spiritual balance between the supernal and mundane worlds is achieved through this burial arrangement.
The symmetry and perfection of the world and its inhabitants, which were brought into existence by The Creator, exist in all of us. This force of balance and union, ignited by our reading, allows the Light of the Shechinah and holy blessings to filter into our world. Our bond to the great Patriarchs, King David and root of our soul, Adam, is strengthened and enriched.