Question: Why is it written in The Book of Zohar that “only jealousy completes the love?”
Answer: Love cannot be complete if it’s not underlain by jealousy. It is written: “Envy (jealousy) of the wise multiplies wisdom.” There are different types of jealousy, but ultimately, jealousy is the revelation of the empty desire that must be filled specifically with love.
We discover empty desires in various states. If the will to receive (Kli) is so strong that there is love being revealed against it, then this desire is the Kli of jealousy. If I desire something, then everything depends on the degree of Aviut (thickness, coarseness) of my desire or attraction. With Aviut Shoresh (0), my desire is weak; with Aviut Aleph (1), it is stronger, and so on, up to the Aviut Dalet (4), when my desire is infinite.
Therefore, every level of desire has a corresponding degree of jealousy, meaning to what extent a person is “burning” with the desire for the lacking fulfillment. And hence, against the love that has to become revealed, there is the empty desire for its revelation: jealousy, a true “hell fire (the fire of netherworld).”
From the 2nd part of the Daily Kabbalah Lesson 10/12/10, The Zohar