It says in The Book of Zohar that Moses asked the Creator for mercy after the death of Aaron’s sons: …if those living in this world will repent and return to You, who will bless them? The Creator answered him: “You are telling Me that? Tell that to your brother Aaron, since he has been trusted with the blessing Above and below, since he is the element of attaining mercy.”
The point is that the contact with the Creator occurs through the attribute called a priest (Aaron) in a person.
A blessing is the descent of the Upper Light in order to correct a person. The Light can only go through Aaron the priest, which means through this hierarchy. It cannot be any other way. It is impossible to come in contact with the Creator any other way.
From KabTV’s “Secrets of the Eternal Book” 3/06/14