From the good side of Cain came Keinan and Mehalel, as mentioned in the Zohar. (Zohar II Terumah 168a) After that, Reuben the firstborn of Jacob was born. He would have received the firstborn rights of Cain, the firstborn of Adam, had it not been for the episode of Bilhah. (Gen. 35:22)

The firstborn right goes part and parcel with guarding the brit [covenant]. Reuven disturbed the bed arrangements of Jacob, which, on his exalted level, was counted as a lack of guarding the brit. Joseph, who was outstanding in guarding the brit, took it over. (Likutei Moharan 2)

Although not mentioned in Scripture, the Midrash tells that Cain took the extra wife of Abel. (Midrash Raba) Here the Ari'Zl reveals that the spark of Cain in Reuben caused him the incident with Bilhah.1

Reuben...used the Cain energy for good...

The name of Reuben comes from "'r'u bain/see the distinction' - between Reuben and Esau." (Gen. 29:32, Rashi) Esau is also from Cain. See the distinction - between Reuben, who used the Cain energy for good, and Esau, who did the opposite. Like Cain, they are both firstborn.

The Rabbis explain that all Reuben did was switch the bed of Bilhah. His intention was to protect the honor of his mother Leah, who was treated somewhat secondary while Rachel was alive. After her death, he reasoned that Rachel's maidservant should not enjoy first level status over his mother. Even though his intentions were good, he was held accountable for having disturbed his father's marital arrangements.

Nonetheless, the scenario shows the spark of Cain making progress. An outright crime graduated to become a subtle disturbance. This is a general theme found in the gilgul process. Just as the metal gets more and more refined each time it goes through the furnace, so are souls purified more and more each time they come back.

This paragraph starts by mentioning that Kainan and his son Mehalel are from the good of Cain – what seems to have no connection to the continuation about Reuben?! Mehalel means ‘praisemaker’. He furthered the good of Cain by being busy, as David, praising G‑d. This empowered the good of Cain to step further in Reuben and open a channel for the revelation of the grand firstborn energies. Even though it was too high to remain by Reuben, he opened a channel for his following offspring to eventually do it completely.2

When he sinned, he also lost the priesthood...

According to the Targum [Aramaic translation of the Torah], the verse "Reuben, you are my firstborn... foremost in s’eis [rank] and foremost in power" (Gen. 49:3) refers to the Birthright, Priesthood, and Kingship. The secret of "s’eis" is that it refers to the Priesthood, which is alluded to with respect to Cain as well. When he sinned, he also lost the priesthood, which is called "s’eis."

G‑d told Cain before he murdered his brother, "If you do well s'eis [you will be uplifted] - and if you don't do well, sin crouches at the door". (Gen. 4:7) The Ari'Zl reveals that this is the source of s'eis that is said by Reuben. The meaning of s'eis is to lift up. The good part of Cain is super-good. The birthright, priesthood, and kingship are the outstanding forms of prominence - being raised up - that are found in the world. SAS-701/s ’e is plus one equals ShBS-702/Shabbos, which is like the world-to-come (Brachot 57b) – the source of all elevation, where the three heads will shine in full brilliance.

G‑d gave Cain a 'heads up' as to what he could merit if he withstands coming tests. This is written in the Torah to call attention to the fact that G‑d does this - in different ways, to varying degrees - for everyone. Also, each person can merit to extraordinary things. Man was made to ascend - and the sky's the limit.

The three forms of prominence are all inter-related. They are all forms of being a head. They come from the three heads that are found in keter (Eitz Chaim) - the head of the sefirot. This itself is the source of the extra-specialty of the good part of Cain.

The patriarchs fixed up the original sin.3 They removed the cover of extraneous material that cloaked the good of Cain. Automatically, the first born of Jacob, the culmination of the patriarchs, found a major expression of the good of Cain within him.

Nonetheless, the tribes were imparted with the job of taking the work of the patriarchs to the next level. Therefore, there still had to be a test for this to express. Even though Reuben as if did not seem to pass the test 100%, the special levels of good were channeled through him and brought into the world. Joseph took the firstborn right, Levi took priesthood, and Judah took kingship. This allows the three heads of keter to come out and do their thing to perfect the universe.

...the whole point of the redemption is to reveal the firstborn aspect...

The unification was later actualized in the people, after suffering the pangs of Egyptian servitude. The first thing G‑d told Moses to say to Pharaoh in his mission to redeem them was, "My son, My firstborn Israel." (Ex. 4:22) This implies that the whole point of the redemption is to reveal the firstborn aspect - in all of its triple facets. "And this shall be the sign that I sent you (to redeem them): When you take the people out, they shall serve Elokim on this mountain (Mt. Sinai, by the giving of the Torah)." (ibid.) The goal of the redemption from Egypt was to be manifest there. And so before the Torah was given it says, " And you shall be for Me a kingdom of kohanim [priests] and a holy nation." (ibid.) " Kingdom " hints to the crown of Kingship. " Kohanim " means the crown of Priesthood. " Holy " alludes to the crown of Firstborn, who is holy. (Ex. 13:2) The three heads were brought together in the entire nation. Therefore, if they had only held on to the level attained by the giving of the Torah, no exile would have followed. (Midrash)

The Forefathers are rooted in Atzilut and they made their tikun there. The tribes took it a step further down and drew the repair to Beriya.4 Then came the seventy soul stage (Ex. 1:5) - out of the seventy sefirot of Yetzira. They exploded into the six hundred thousand of Egypt, (Num. 1:15) who operate out of Asiya. To this day, their offspring fix in this world.

[Translation and commentary by Perets Auerbach.]