?Why was the eighth day after the birth chosen for the Brit

In the Kabbala we find two methods to understanding the meaning of the number eight. One method looks at our world and finds it built like a six sided cube: up, down, and the "four corners" of the world. These six sides border the natural world, which was created in six days and their existence is dependant and "standing" upon the inner point – the Sabbath Day, the source of the spiritual flow which gives life to all the worlds, and sustains them since the first days of creation 

If all the corners of creation are the six days and the inner source is Shabbat, where is the eighth day? Outside. Above nature, beyond the borders of the natural cube

In light of this method, we can understand the meaning of the Brit as a spiritual connection above our understanding, a wonder beyond anything humanly graspable in light of the borders of nature

A different method, and maybe even an opposite method, sees the seven days of creation as a creation of God. Truth be told, the secrets of Creation are a mystery to us all

Many theories regarding the creation of the Universe rose and fell, and no scientist can positively say he knows the secret of creation. After the creation of world, after the first Sabbath, started the eighth day – and with it a new chapter in Man's existence, who was released from the womb of creation and entered this world in order to complete his mission and be a "partner" with God in the rectification of this world

 According to this method, we can see the Brit as the first step in Man's task of rectifying this world. Actually, is there really a big difference between the two methods? Isn't the fact that God designated us, mere mortals made of blood and flesh, with such a lofty mission as rectifying the world, the greatest wonder that we could think of