And he lay with her that night (Vayetze)

"And Yakov slept with Leah that night... and Issachar was born."

Issachar studied Torah more than any other of the twelve sons of Yakov. So, Issachar represents the essence of Yakov. It says "that night" and not "on that night." In Hebrew, it is "ba laila who" and not "ba laila hawho." The word "that" applies to the man (Issachar) and not the night. 

Later, Issachar was reincarnated as Rabbi Akiva. When the brothers sold Yosef, and the time came to atone for that, Rabbi Akiva was the leading sage of the ten sages martyred to perform this atonement. The connection to Issachar is in the words of Rabbi Akiva.

Now, we can establish other connections. Adam had two wives: Lilith and Eve. Adam's reincarnation, Yakov, also had two wives, Leah and Rachel. Yakov's reincarnation, Rabbi Akiva, also had two wives: the former wife of Turneius Rufus and his first wife, Rachel. The wives are also connected through reincarnations.

Art: Joseph sold by his brothers by Balthasar Beschey