Crushing Olives/the Body/Forgetfulness Produces Torah
Likutei Halachos on Parshas Tetzaveh
Translated by Dov Grant
Possuk 27:20 "…they shall take for you clear, mortar pounded olive oil for illumination"
The kezayis (volume of an olive) is the standard measure of food in the Torah. This is the quantity that obligates one in birchas hamazon and other concluding berochos. This distinction of the olive is due to the fact that the olive and its oil teach about the concept of the body and its nefesh (life force), corresponding to the concept of forgetting and memory. For chazal tell us that eating olives causes memory loss, whereas consuming olive oil is beneficial for the memory. Therefore the olive and the oil contained within it correspond to the concept of forgetting and remembering, itself an aspect of body and nefesh. And the nefesh, which is an aspect of memory, corresponds to the Torah, which is an aspect of knowledge.
Therefore, the kezayis is the standard Torah measure. For the Torah, which corresponds to the nefesh, an aspect of memory, corresponds to the olive and its oil. For the oil "clothed" within the olive corresponds to the memory "clothed" within forgetting, which is an aspect of the nefesh that is "clothed" within the body.
And just as it's only possible to reveal/extract the oil for illumination through pounding, similarly the only way to reveal the Torah/nefesh/memory is by "pounding and beating" [i.e. physically depriving] the body. For this pounds and breaks the frustration of physical matter and annuls and subjugates the power to forget. Then the light of the Torah, the nefesh and memory is revealed from within the body/forgetfulness, by result of the relative annulment of the body/forgetfulness in respect to the nefesh/Torah/memory.
Chazal express this idea as: "The Torah is only preserved through someone that 'kills' himself over it” (i.e. that one must 'kill' oneself to learn Torah by "beating and breaking" the body). Only in this way can the Torah/nefesh/memory be revealed. This is expressed by the verse "clear, mortar pounded olive oil". And this corresponds to the statement of the Zohar (II 168a) that "wood that hasn't been removed can be engulfed in flame, but a body that hasn't been removed [i.e. died] can be suffused with the light of the soul".
Thus, the olive and olive oil correspond to the body and its nefesh. Therefore, all Torah measurements are a kezayis, since all Torah mitzvos are performed through the body and nefesh, i.e. when the nefesh is clothed within the body. Then is the main preservation of Torah, since the main revelation of the Torah and the nefesh is from within the body – corresponding to the concept of "the gain of light over darkness" as explained elsewhere.
Likutei Halachos Orach Chaim Hilchos Birchos Hapeiros 3-4