זוהר בראשית — דף קנח ע”א

Whoever occupies himself with Torah inherits the World to Come and the inheritance of Jacob, for “Issachar” means “there is a reward.” Rabbi Ḥizkiya explains that Leah’s six sons are above, below and the four sides of the world; they are the “mountains of spices,” as opposed to the “mountains of Bether,” mountains of separation; the sons of the maidservants are four knots. Rabbi Elazar asks why Jacob wanted to leave when Joseph was born, and answers that, as explained, Esau’s adversary had been born; Joseph completes the body and Benjamin the count of twelve. When Benjamin is born, Rachel dies and takes the house; Leah did not die then, because her deeds are hidden. Leah was buried in the Cave of Machpelah, in concealment, and Rachel on the open road.