The three lines are the core of the work of Malchut, the desire that builds itself in the likeness of the Creator. The right line is bestowal, the left line is receiving, and the middle line is their union in similarity with the Creator.
Question: We can say that the left line is my natural desire. The right line is a force that is outside of me that I must summon upon myself. When they merge with each other, do you get the third line?
Answer: There are many different types of middle line. That is one of them.
Question: In Kabbalah, there is also the term “12 tribes.” When speaking of the 12 tribes, everyone begins to imagine some people divided into tribes. From the Kabbalistic point of view, are we talking about three lines multiplied by the four-letter HaVaYaH, which ultimately gives 12?
Answer: Yes. It is the most complete HaVaYaH: four stages, three lines in each, which makes up the 12 tribes or a special kind of work of creation.
From KabTV’s “Fundamentals of Kabbalah,” 6/17/19