Every person has a soul on the level of ohr makif [surrounding light] - the part of the soul not contained within any type of vessel, that is, a body, and an ohr pnimi [internal light].

When Nadav and Abihu were born into this world, the[primary] tikun for the root of Cain began, the second and superior level of root from Adam. All the souls of this root came from the tzelem [image] of Nadav and Abihu, on the level of the ohr makif [which rests] on them.

The soul and the body are intrinsically opposites. In order for them to be able to get together, there must a kind of intermediate category that draws from both. (Likutei Torah Baal HaTanya) This is the secret of the tzelem. The soul becomes clothed in a sort of quasi-spiritual organism (astral body) that affords it the ability to enter a body and dwell within it. It has an aspect of surrounding light that accompanies the person.

These souls began their repair process with the birth of the first two, greatest sons of Aaron. (Zohar III)

However, all of these souls were still not purified - only the two sparks of Nadav and Abihu themselves. The rest of the souls of this root, included in the tzelem of the ohr makif of Nadav and Abihu, still contained evil kelipot.

When a soul comes into this world that was previously from the tzelem of Nadav and Abihu, it [thereby] becomes purified from the kelipot.1 The remainder of the souls of this root which are part of the tzelem from which this newly purified soul came remain amongst the kelipot. Thus, when a soul is purified and redeemed from within the kelipot and enters this world, the rest remain impure and part of the tzelem, in the secret of the ohr makif of the soul that was already purified.

They 'hop on the bandwagon' of the newly cleansed soul. This is a step to help them also attain purity.

As mentioned previously, the purification of a soul and when it comes into this world is not based upon its spiritual level, rather upon the situation created by man below. He determines the type of soul that will be drawn into his seed, as mentioned before in previous discussions.

Sometimes, a very elevated soul will remain sunk in the kelipot for a long time, unable to exit until a certain merit related to its leaving can be arranged. Less-elevated souls can exit and enter this world even prior to others, because of a merit that was performed connected to their leaving.

Based on the soul's root in the 613 commandments, it requires certain specific mitzvot to be a merit for it in order to be liberated from the sitra achra.

Sometimes, a person may transgress in this world, and the kelipot will want to destroy him and draw him astray. At that point, they will draw a soul from his root to him, one which is sunk in the depths of the kelipot and full of chitzonom [outside energies]. They draw it out and it becomes like a tzelem for the person who transgressed, causing him to sin more.

Being from his root and spiritually attached to him, it has the ability to steer him astray. This is a kabalistic example of how "the reward of sin is sin". (Pirkei Avot 2:1) The person is held somewhat responsible for the damage which the extra soul caused him to do because he drew it upon himself through doing the wrong things,

The inner workings of this aspect of Providence are based upon "A person is led in the way he wants to walk". (Makot 10b)

However, it can be that the soul they draw to him will be a great soul which happened to be immersed in the depths of the kelipot but [that] the kelipot assumed was already destroyed and unable to return to its former state. Instead, G‑d will help it, arouse it from amongst the kelipot, and reveal its strength and holiness. As a result, it will instead help the person to do good.

This is the secret of the verse, "The time when ha'adam [the man] exerts power over his fellow to his disadvantage": (Eccl. 8:9) The time when "ha'adam habliya'al [the despicable man]" - of the kelipot - exerts power over his fellow - the holy soul. However, in this case he made a mistake, for what he thought was to the benefit of the kelipot turns out to be just the opposite, as the Saba of Mishpatim explains. Afterwards, this soul itself (from the kelipot) will become purified and will also come into this world.

Providence does this to as if 'trick' the sitra achra and bring about its designs.2

Although G‑d is G‑d (Ex. 3:14) and He can always do whatever He wants, He created a system with rules that He usually chooses to abide by.3

[Translation and commentary by Perets Auerbach.]