The father gives a portion of his soul to the son, and the teacher gives part of his spirit to the student.
It makes no difference: if a man marries his soul mate or if he takes another woman who is not his soul mate, he can father children that are sparks of souls from his own root, or souls from a different root.
The father gives a portion of his soul to his children.
The mother also gives a portion to her children, but her role in gilgulim is not as relevant as that of the father.
This portion becomes an exterior garment to the soul of the son.
According to the Kabbala, everything in Creation has two aspects: "Light" and "Vessel". When we are talking about humans, for example, these two aspects are called "body" and "soul". When we are talking about partzufim, the aspect of Light is usually called "mochin", but here we are going to also use the original term "Light". (Actually, the Light itself has three aspects: Light, mochin and tzelamim-images, but these details do not concern us here.)
Although everything has these two aspects of Light and Vessel, there is another third aspect, which lies intermediate between the Light and the Vessel. It is called the "Levush", or "Garment", because it is an external garment to the Light. This garment is interior to the vessels which comprise the limbs of the partzuf, but it is called Levush because it is the garment of the Light and Mochin. It covers them and dims them to eliminate the possibility that the vessels might break because of the great magnitude of light entering into them. The father gives a portion of his soul to his children…
This Levush or garment is actually the NHY (the sefirot of netzach, hod and yesod) of the Higher Partzuf. For example, let us say that the Lower Partzuf is Zeir Anpin. We will call the Higher Partzuf "Imma", but in the realm of the soul this description applies to the relationship of father and son as well. (See Otzrot Chaim, Aifah Shelaimah, p.34a, bet.)
The light of Imma that is within its three lower sefirot, NHY, ascends upward into its own tiferet, leaving the vessels of NHY empty. Then the Light or mochin that is being transmitted to Zeir Anpin from above through Imma enters into the vessels of NHY of Imma. The vessels of NHY of Imma become the garment for the Light of Zeir Anpin, and in that configuration they enter into the Vessels of Zeir Anpin.
Afterwards, Imma grows new NHY for her own Light of NHY.
The ChaBaD of the Light of Zeir Anpin enters into the ChaBaD of the Vessels of Zeir Anpin.
The ChaGaT of the Light of Zeir Anpin enters into the ChaGaT of the Vessels of Zeir Anpin.
The NHY of the Light of Zeir Anpin enters into the NHY of the Vessels of Zeir Anpin.
However, the Garment of the Light of Zeir Anpin, which is the NHY of Imma, is always situated between the Light and the Vessels.
(A section of Etz Chaim, Gate 20, Chapter 3, is relevant to this description.) Each of the Nefesh-Ruach-Neshama has five partzufim, and each partzuf consists of 613 limbs…
In our text the Arizal wrote, "The father gives a portion of his soul to his children, and this portion becomes an exterior garment to the soul of the son." The portion that was part of the father's soul is the NHY of the father's soul. It becomes a garment for the soul of the son. (See Appendix 20:3.)
(This portion that became an exterior garment to the soul of the son) helps him and guides him down the proper path. For this reason, a son is obligated to honor his father.
The father gives up a part of himself for the sake of his son. Therefore, the son is obligated to honor the father.
However, if there is less than five hundred levels difference between the soul of the father and that of the son, then the portion of the father's soul will remain with the son's even in the time of Mashiach.
We have already learned that each of the NR"N (Nefesh-Ruach-Neshama) has five partzufim, and each partzuf consists of 613 limbs. These are called "major roots".
Now, it will be explained with the help of G‑d in Gate of Reincarnations 11:2 that each one of these limbs, or major roots, has 600,000 branches that are called "minor roots." Each spark is a whole soul in itself that must enter the world in gilgul, each one in its time, in order to achieve tikun…
In addition, each one of the 613 major roots consists of 613 sparks. These are called "major sparks," and they may divide into 600,000 minor sparks, according to need.
Thus, there is a maximum of 613 x 600,000 minor sparks in each and every partzuf. This number, by the way, is 367.8 million. Each spark is a whole soul in itself that must enter the world in gilgul, each one in its time, in order to achieve tikun.
Thus, each one of the roots and sparks of each partzuf have a place, or level, in the general hierarchy of souls. The levels of two different souls may be close to each other in this hierarchy, or far apart. If the distance between them is more than 500 levels, then the portion of the father's soul given to the son will remain with the son's soul even in the time of Mashiach.
Nevertheless, in the time of Resurrection of the Dead or in the World-to-Come everything returns back to its root. They will separate completely.
If there is less than five hundred levels difference between the soul of the father and that of the son, they will remain together even in the time of Mashiach. However, in the time of Resurrection of the Dead or in the World-to-Come, when everything returns back to its root, they will separate completely.
On the other hand, if there is a difference between them of five hundred levels, or more than five hundred levels, then the lesser will be nullified within the greater. They will permanently unite forever, and they will never separate. The two of them will become one root.
This is in regards of a father with a son. A teacher gives some of his spirit to his student…
Regarding a teacher and his student, we have already explained that a teacher gives some of his spirit to his student, like a father does to a son.
This does not refer to the Ruach (often translated as "spirit") that is one of the NR"N. Rather, it refers to a minor ruach. In effect, the Arizal does not consider the information transmitted by the teacher to the student as a mere ethereal, non-entity. Rather, it is something that is real; it has content and substance, and it endures forever.
However, it is a more forceful connection. The spirit stays with the student forever, and they never separate. This is the esoteric meaning of the joining of the Nefesh of David with the Nefesh of Jonathan.
The joining of the souls of David and Jonathan was also mentioned earlier in 3:1 in a different context. It was based there on the verse from Samuel I 18:1. Here, the connection to the verse is more general and less explicit.
This is the reason that more respect is due to a teacher than to a father.
There are many laws in regarding respect due to a teacher and to a father. The teacher referred to here is called a "Rebbe Muvhak," which is defined as someone from whom the student has learned most of his wisdom. In our generation it is very difficult to imagine the relationship between a student and a Rebbe Muvhak.
In general, more respect is due to a teacher, i.e. a Rebbe Muvhak, than to a father. For example, if a person's Rebbe Muvhak and father were both captured by pirates, and he only has money to redeem one of them, then the Rebbe Muvhak takes precedence. It is the same if he can only save the lost or stolen property of one of them. The Talmud provides a simple reason; one's father has given him life in This World, while one's teacher gives him eternal life in the World to Come. (Baba Metzia 33a, and see Book of Knowledge, Rambam, "The Laws of Talmud Torah," 5:1)
However, there is an exception to the rule, when the father is also a scholar, and all the more so if he is also the son's teacher or the teacher's teacher.
What is the case if the teacher of the student is also his son? Then they are doubly bound together, because the same one is his teacher and his son. If there is less than five hundred levels difference between them, then they are (permanently) bound together to each other.
This is according to what was taught in this section previously: "If there is a difference between them of five hundred levels or less…they will permanently unite forever, and they will never separate. The two of them will become one root."
The father (is bound) with the son because he (the son) is the teacher, and the son is bound with the father because he is his father. The two are bound to each other, this one to that one, and that one to this one, from both sides.
In one respect this one is higher, and in another respect that one is higher. Nevertheless, they bind together, become one root, and "the lesser will be nullified" and subsumed within the greater.
[Commentary by Shabtai Teicher.]