זוהר שמות — דף ו ע”א

Rabbi Hiya questions Rabbi Shimon on why the Torah counts the sons of Jacob first as twelve and then as seventy. Rabbi Shimon explains: twelve corresponding to twelve celestial princes, and seventy corresponding to seventy princes. Israel is bound to the higher beings and sustains them. The soul is a divine portion from above, and it is about this that the Holy One said 'we will do and we will hear.' The seventy souls of Jacob's household who descended to Egypt correspond to the seventy celestial princes, to contend with them.