My teacher also taught me that three erred regarding the end of days: Jacob our forefather when he called his sons together and told them, "Gather together and I will tell you what will happen to you at the end of days" (Gen. 49:1) and it was hidden from him. (Pesachim 56a) Samuel the prophet was the second, for regarding Eliav he said, "Surely before G‑d is His anointed" (Samuel I 16:6) as if to say from him Mashiach would come. Rabbi Akiva was the third, because he thought Bar Koziba was Mashiach of G‑d. Thus, the letters of Jacob/Ya'akov are in Akiva, because their error was the same, and the three of them had to reincarnate to rectify this mistake.

...the three of them had to reincarnate to rectify this mistake.

The final end is drawn from keter and all of its three parts - led by the highest head - Raisha D’lo Ityada [the Unknownable Head]. Therefore the time and way it is to come is unknowable. This energy was established to come to the world, and through the descendants of Abraham, when Isaac gave the blessings to Jacob. Therefore, Providence set it up precisely in such a way that Isaac did not know that it was Jacob at the time. (Gen. 27)

Jacob ascended to this place in his departure, but the Shechinah left when he tried to reveal it, for the world is not there. Trying to bring in it is too much light which is detrimental.

The messianic potential is innate in Yishai, who paved the way by being from the four super tzadikim who never sinned. (Shabbat 55b) It was to come out in his sons, and Samuel was sent to do the task. G‑d did not at first tell him which of the sons it was. Again, because Mashiach comes from Ra"DLA and is above grasping. Samuel thought that it was Eliav. Until it was revealed that the least expected last son of Yishai, David, is the one.

Rabbi Akiva saw the Mashiach spark in Bar Kochva...

As mentioned, Rabbi Akiva saw the Mashiach spark in Bar Kochva. But he at first didn’t see that it was not able to fully then manifest because the world was still not ready.

These three tzadikim that touched the level of the final end had to so specifically, as if, err in order to draw a bit of Ra"DLA/not knowing mechanics into the world to prepare it for Mashiach, when he will finally come ‘b’hesach had’a’at’ [unexpectedly]. (Baba Metziya)

My master also taught me that sparks from the root of Cain were within the kelipot of Sisra, and for this reason Ya’el drove the spade through his temple (Judges 5:26) since that is the place of the moach of da’at of chesed and gevura, from which the root of Cain comes, as said earlier. Even the spark of Rabbi Akiva was there, which is why he was born from the children of Sisra.

From this episode comes one of the songs of Scripture, the song of Deborah. Cain is the father of Yuval, who brought music to the world. (Gen. 4:21) Music is the primary way of fixing his root, and for this, David is the "sweet singer of Israel". (II Samuel 23:1) Deborah was a female judge/leader, and this miracle came about through Ya’el, a lady. In the aspect of "a woman of valor is the crown of her husband". (Prov. 12:4) "But your glory shall not be complete, for G‑d will give Sisra into the hand of a woman". (Judges 4:9) This is the typical Cain/left side/Nukva-feminine aspect.1

"And G‑d made for Cain a sign..." (Gen. 4:15) The original mistake of Adam planted a selfish brazenness in man. This dirt of the snake went mostly to Cain, who came out first. (Zohar) This led him to murder his brother. When he repented, the brazenness was circumcised away and he acquired the holy opposite quality of shame. This manifested in the forehead and is the holy sign that G‑d made for him. (Likutei Moharan)

Still, the bad part of Cain was not completely fixed and goes through many reincarnations to be refined. It was in Sisra and caused him to have the chutzpah to start up with the chosen people. Therefore Ya’el drove the spade into his forehead, the place of the Cain’s sign after repentance. Here the Ari.Zl. tells that it is one of the places of his soul-root - which explains why G‑d chose it to be the place of the sign of Cain’s teshuvah.

The teshuvah of Cain aided Ya’el to kill Sisra...

The teshuvah of Cain aided Ya’el to kill Sisra, subjugating the enemy and allowing the people to rout them. She therefore was the wife of Chever the Kainite, who is from the good of Cain.

My teacher also told me that ABYY/Abaye was Rav YYBA/Yaiba Saba of Mishpatim, and that Abaye is alluded to in the head-letters of the verse, "Only against me did He turn His hand". (Lamen. 3:3) It says "turned" to allude to the reversal of Yayvo to Abaye. This is the "turning of His hand," for the Y/yud's changed to the end of his name. My master did not want to reveal to me the reason for the reversal.

[Translation and commentary by Perets Auerbach.]