זוהר שמות — דף קי ע”א

The Saba discusses the secret of the Eitanim and the Mountains: the Patriarchs are the Eitanim of the world and the month of the Eitanim is Tishri. Abraham is called Eitan ha-Ezrahi and the river flowing from Eden is called Mashkil le-Eitanim. The three upper levels are the Mountains, and the three lower ones are the Eitanim, foundations of the earth. The month of Tishri is the month of the Eitanim when the Patriarchs were born and when all Israel gathered to Solomon the king.