Question: What symbolizes the correction in three lines?
Answer: Correction in three lines is the ability to differentiate the influence of the Light, the desire to bestow (right line), from the influence of the desire to receive (left line), and the ability to be in the middle between them, in order to couple them and connect them together in the middle line.
If a person works in above reason in order to connect his vessels of reception with the force of bestowal that exists in him, this means that he is the middle line, in his middle point and is doing corrections in three lines.
In this case, he does not use his real Malchut, but only Malchut that rises to Yesod. It means that he scrutinizes the vessels, which will be in the correct connection and participation of Malchut and Bina. Correction in three lines is possible only after the second restriction (Tzimtzum Bet) when it is clear to us that Malchut is not capable of receiving any Light in herself, but only under the condition that she rises to the level of Bina. (Rising in spirituality symbolizes correction.)
At the time that Malchut rises to Bina, they partially connect. Malchut clarifies which of its qualities it can use in order to be in contact with the Light, with the Keter.
In order to be similar to Keter and to be bestowing like the Keter, it must connect with Bina and become similar to her, the same as Bina. At the time of Bina expanding from top to bottom, she wanted to be similar to Keter with all the depth of her coarseness (Aviut). A correct joining between Malchut and Bina brings Malchut to the calculation in the middle line.
It cannot be a prayer (MAN) without correction of three lines. However, the upper receives our prayer the first time when we request the first contact and are ready to turn into a spiritual fetus that annuls and restricts itself completely. Meanwhile, we don’t have correction of three lines. But later we start the period of the “three days of the absorption of semen” in which the three lines: right, left, and middle are created. From here onward begins the development of these three lines.
From the 3rd part of the Daily Kabbalah Lesson 1/29/13, The Study of the Ten Sefirot