Even someone who is presently completely wicked and on the lowest level can change himself to become a very righteous person, and this is possible because of the revelation of Hashem’s encompassing Light in this world.
This is the meaning of what our Sages said, (Pirkei Avos 4:17) “One hour of Teshuva and good deeds in this physical world is better than all of the life of the spiritual World to Come.”
This is because “the life of the spiritual World to Come” is only from the aspect of how Hashem’s revelation is “מְמ ל א כ ל ע לְמ ין-permeates all worlds,” which is expressed through limiting and restricting the Light to what each creature can handle, like it says, (Menachos 29b) “The World to Come was created with the letter ‘י-Yud.’” Just like a י' is shaped like a dot, so too, Hashem’s Light had to be shrunk down to the smallest point in order to be internalized within each of us, according to our capacity.
However, the Torah and good deeds that we perform in this physical world are from the aspect of how Hashem’s revelation is “סוֹב ב כ ל ע לְמ ין-encompasses all worlds” equally beyond all limitations.
This is the main purpose for which the divine soul came down to become invested into a physical body: Only in this physical world is there an expression of how Hashem’s revelation is “סוֹב ב כ ל ע לְמ ין-encompasses all worlds,” which enables it to refine and transform the animal soul and body from bad to good.
The number of years of life is allotted to each person according to this goal. To one person, 70 years; to another person, 80 years, etc. Each according to the amount that he needs to refine and transform from the animal soul and body from bad to good. Every day, a person refines and transforms another portion, so that throughout the years of a person’s life, he completes the process of refining everything for which the soul came down into this world.
The Alter Rebbe explained how specifically because of Hashem’s “encompassing Light” being expressed in this physical world, we are able to transform the body and animal soul from bad to good through Teshuva, Torah, and Mitzvos. The focus is on how Mitzvos can refine and transform the physical body and animal soul, since Mitzvos are the recipients of the “encompassing Light.” (Torah study, by contrast, exists in the spiritual world too, where the “encompassing Light” is not expressed as much).
