Our Gemara on amud beis makes a linguistic observation in regard to a teaching that referred to “great halachos”. The Gemara comments that if they are described as “great”, there must also be halachos that are considered minor, which it finds odd, since can any halacha be considered small? Therefore, the Gemara rejects and revises the text of that teaching.
But we must ask ourselves, on a practical level, aren’t there halachos that are more serious than others? No legal or moral system can operate by treating everything with equal priority (see Tosafos Yom Tov on Avos 2:1). Additionally, the Gemara (Chullin 142a) describes certain mitzvos as lighter, such as sending the mother bird away, as it incurs minor cost and bother.
Mishna Avos (2:1) tells us:
וֶהֱוֵי זָהִיר בְּמִצְוָה קַלָּה כְבַחֲמוּרָה, שֶׁאֵין אַתָּה יוֹדֵעַ מַתַּן שְׂכָרָן שֶׁל מִצְוֹת
Be careful with a light commandment as with a grave one, for you did know not the reward for the fulfillment of the commandments.
This statement is confusing and contradictory. If one mitzvah is lighter and the other more serious, but yet they should be treated with equal caution, how can one be lighter and the other more serious?
A simple reading of this Mishna might be as follows: Though some mitzvos have greater punishments or severity than others, treat them all the same, because since we cannot understand the reward for even a minor mitzvah, we would not want to let even the smallest one go by. In fact, Midrash Shmuel (ibid) says something similar. However, there are other compelling answers, each one providing meaning in a different way.
Rambam (ibid) says a logical answer, which is that the Torah quantifies various punishments for prohibitions, and therefore it is obvious that one that incurs death is more severe than a simple prohibition. The Mishna however is referring to positive commandments, of which it is impossible to determine which is more important. The Rambam elegantly proves this from the principle that when one is involved in one mitzvah, he is exempt from another, and no equation is made to determine if the second mitzvah is more important.
Kedushas Levi (Bereshis 21) explains that the so-called light and heavy mitzvos have to do with how frequent there is opportunity for the mitzvah. Thus, a light mitzvah is prayer or Torah study which is daily, versus the mitzvah of succah or matzah, which is annual. We then read it as “scarce” versus “routine”, instead of light versus heavy, and Avos is instructing a person not to take a frequent mitzvah for granted.
Chiddushei Harim interprets light mitzvos versus heavy, as referring to the standard default reward. However, in each situation, there is a subjective reward and punishment based on the person’s particular circumstances. Therefore, one should treat a light mitzvah with the same severity as a heavy one, as it is unknown what the effects will be for him.
Maharal (Tiferes Yisrael 61) offers a different idea. He says that there are mitzvos that are easier to do, and harder to do. In that sense, there is absolutely a greater reward for mitzvos that one must work harder to achieve, as it says elsewhere in Avos (5:23), “The greater the hardship, the greater the reward.” However, there is also an intrinsic reward and value to each mitzvah that is beyond the human ken, and may not be in line with our subjective logic. We can think of this by way of the following metaphor: A lay person might believe such a food is healthful and another food is harmful, but an expert physician might have a different perspective and evaluate the harm and benefit differently, based on his knowledge of the scientific facts. Similarly, Sefer Baal Shem Tov (Va-Eschanan 5) learns from a play on words “careful” in Hebrew “Zahir”, which also means to shine. One can get a greater enlightenment or glow from an apparently light mitzvah than an apparently heavy mitzvah.
I will conclude with a fascinating notion that can also be used to interpret this passage. The Ishbitzer (Beis Yaakov Vayechi 26) says every Jew has one mitzvah that is somehow tied deeply and extraordinarily to his neshama. A Tzaddik cannot break with such a mitzvah that is tied to his Neshama, no matter what, and must even martyr himself though not from the standard three sins that all must give their life for.