The Zohar, Chapter “BeHaalotcha (When You Mount the Candles),” Item 10: This is so in action, meaning in sacrifices.
Item 11: When the priest intended to light candles below and bring the incense closer, the upper candles, the Sefirot, would shine at that time, everything was connected, and joy and jubilation were in all the worlds, as it is written, “Ointment and perfume delight the heart.”
The main spiritual work is sacrifice, where the word “sacrifice” (Kurban in Hebrew) means “closer” (Karov). This means that we take our desire to enjoy, measure it, and check to see which part can be the “sacrifice.” By “slaughtering it,” we bring it closer to the quality of bestowal, releasing it from its egoistic form of “an animal” that lives only for its own sake.
We want to raise it to the level where it can be used by man, elevating it from the animate to the human level. This is the essence of all sacrifices from the still level (salt and water), the vegetative level (grains), and the animate level (birds and animals), which are the levels that are brought to the Temple. It is the corrected Malchut, where Malchut is connected to Zeir Anpin.
All of this is talking only about desires inside a person, which are corrected from egoistic to altruistic. It seems like it is talking about hard, dirty, and cruel work, such as sacrificing or killing with blood and water. And indeed it is – the correction of our egoistic desire is dirty work. It is written, “Mother (Bina) will come and cleanse the son.” This is why we need to attract the Upper Light so that it works on us. Then, the work is done by forces of Cohen, Levi, and Israel: singing, blowing the horn and lighting the candles – the Sefirot that shine from Zeir Anpin into Malchut. A person does not have to know all the details of this work; once he receives these qualities corrected by the Surrounding Light, he will see how it all works. We only need to observe the Creator; He will wage this war with Pharaoh, while we simply have to want it.