The pasuk says:
וּשְׁמַרְתֶּם אֶת־חֻקֹּתַי וְאֶת־מִשְׁפָּטַי אֲשֶׁר יַעֲשֶׂה אֹתָם הָאָדָם וָחַי בָּהֶם – You shall observe My statutes and My laws for when a man performs them, he will live by them. (18:5)
The Sfas Emes wonders what the prescribed manner to live by the mitzvos might be.
On the one hand, the Mishna in Avos (2:1) says הֶוֵי מְחַשֵׁב הֶפְסֵד מִצְוָה כְּנֶגֶד שְׂכָרָהּ – Consider the loss through a mitzvah against its reward; on the other hand, the Mishna earlier on (1:3) says אַל תִּהְיוּ כַּעֲבָדִים הַמְשַׁמְשִים אֶת הָרַב עַל מְנַת לְקַבֵּל פְּרָס – Do not be like servants who serve their master in order to receive reward.
This poses a dilemma – are we meant to value the reward, or not?
In order to reconcile these contradictory Mishnayos, we need to gain an understanding of what the ultimate reward for performing mitzvos. The Sfas Emes explains that the reward for a mitzva is not related in any way to anything we can experience. The next world is not physical. The next world is not even a place; it is a state. It is the state of our soul being close to God, something we cannot being to relate to, as everything we know is entirely physical.
In fact, the word for world – עוֹלָם – has the same root as the word for “concealed” – הָעֳלַם. The next world is concealed from us because it is beyond our life experience. In this world, the physical hides God from us. The truth is concealed by the illusion that there is no reality other than this physical world. This is why metaphors such as lies and darkness are applied to this world. In exactly the same way that God is hidden from us in this manner, so is the World to Come. It is the world of light, truth and reality – we have no grasp of understanding what is beyond the illusion.
The reward of a mitzva is being close to Hashem – we cannot relate to Hashem on this World, so intrinsically, the reward cannot be in this world. Performing mitzvos in order to come close to God is the reason we have the mitzvos, and the reason the world was created. It follows that the purpose of the mitzvos and their reward is one and the same. Accordingly, Chazal ask us to consider our loss from performing a mitzvah against the reward. The reward is closeness to God, which is the purpose of the mitzvah, and ultimately, life itself. We thus see that הֶוֵי מְחַשֵׁב הֶפְסֵד מִצְוָה כְּנֶגֶד שְׂכָרָהּ refers to the spiritual reward in the World to Come.
The other Mishna that warns us not to perform mitzvos in order to receive a reward does not mention שָׂכָר; it mentions פְּרָס. Here, Chazal are not referring to the ultimate reward and purpose of the Torah, mitzvos and life. Rather, they are referring to performance of mitzvos for personal gain.
The reason this is so is because the word word פְּרָס is related to פְּרוּסָה – a piece – which implies a separation. Personal benefit and gain are separations and distinctions between ourselves and others. Chazal thus warn us that it further separates a person from the source of life, from God. This is the opposite of וָחַי בָּהֶם – to live through them – as the point of life was to become close to God, but this causes a seperation.
The Sfas Emes has explained that the Mishnayos were not contradicting each other at all – the World to Come is where we become close to God, the point of existence. Everything we do should revolve around that end goal. If personal goals corrupt our actions, we become corrupt and this is what we are advised against.