(source — strongly recommended)
Inspired by the discussion in the comments to this post. An excerpt from here:
The biblical commandments are the 613 mitzvot explicitly or implicitly contained in the Five Books of Moses. The rabbinical commandments are the laws instituted by sages throughout the generations. (For example, praying three times a day, reciting kaddish after the dead, making a blessing before eating, lighting Shabbat candles, and the festivals of Chanukah and Purim are all rabbinical institutions. Indeed, a major part of what we call "Judaism" is of rabbinic origin.)Another excerpt, from here:
Both are equally binding upon the Jew. The sages institute their laws by the divine authority expressed in the verse: "And you shall observe all that they shall instruct you" (Deuteronomy 17:10). Thus, the blessing recited before the performance of a mitzvah -- "Blessed are You, L-rd our G-d, King of the Universe, Who has sanctified us with His commandments and commanded us to..." -- is recited over rabbinical mitzvot as well. G-d is the sole commander of a mitzvah, whether it is written or alluded to in His Torah, or instituted by human beings to whom He imparted the authority to interpret and safeguard His laws and legislate Jewish life.
Nevertheless, Halachah (Torah law) distinguishes between biblical and rabbinical laws, applying a different set of standards to each of the two categories. One of these differences is that, according to many halachic authorities, biblical laws define the nature of their object, while rabbinical degrees are only prohibitions upon the person. For example, if biblical law forbids a certain food, this indicates that the very substance of the food is intrinsically negative and profane; on the other hand, rabbinical proscription of a certain food is strictly a prohibition upon the person not to eat it.
At first glance, this seems to indicate that rabbinical mitzvot are less "real" than biblical ones; that while the biblical law affects the very nature of its subject, the rabbinical law is superimposed over human life, having the authority to command and instruct but not to define reality. On a deeper level, however, this alludes to the fact that the rabbinical law is the more profound expression of the essence of the mitzvah as divine will.
The biblical mitzvot define the nature of our world, expressing the fact that their predominant element is the mitzvah's role as molder and illuminator of the created reality. Not so the rabbinical commandment, which is concerned only with what man should or should not do, not with how this affects him or his world. Thus it asserts the "decree" element of the mitzvah: the mitzvah as it transcends all relation to physical life, its sole purpose being the fulfillment of a divine desire.
In the third chapter of Ethics of the Fathers, the mishnaic sage Akavia ben Mahalalel teaches:
"Reflect upon three things and you will not come to the hands of transgression. Know from where you came, where you are going, and before whom you are destined to give a judgment and accounting. From where you came -- from a putrid drop; where you are going -- to a place of dust, maggots and worms; and before whom you are destined to give a judgment and accounting -- before the supreme King of Kings, the Holy One, blessed be He."
The Mishnah is known for its concise wording -- every extra word or phrase is interpreted by the Talmud to enfold many layers of meaning and instruction. On the face of it, the above-quoted Mishnah is just using lengthy, repetitious wording to convey a single idea. Upon closer examination, however, the Mishnah includes three sentences, which can be interpreted as three separate messages:
1) "Reflect upon three things and you will not come to the hands of transgression."
2) "Know from where you came, where you are going, and before whom you are destined to give a judgment and accounting."
3) "From where you came -- from a putrid drop; where you are going -- to a place of dust, maggots and worms; and before whom you are destined to give a judgment and accounting -- before the supreme King of Kings, the Holy One, blessed be He."
The Lubavitcher Rebbe explains that Akavia ben Mahalalel is in fact speaking to three different types of people: the materialist, the spiritualist, and the tzaddik.
The third and last part of our Mishnah is addressed to the materialist, who sees nothing higher -- indeed nothing other -- than the body and its needs, wants and desires. It's all but useless to speak to the materialist about his soul. So we talk to him about his body -- about the fact that it's nothing more than a bag of flesh with a slimy beginning and a maggoty end, and that there's a higher authority before which it will one day be taken to task for all it did during its earthly life.
The second and middle part of the Mishnah is addressed to the spiritual person. To him, we need not speak of the lowliness of the body; instead, we extol the virtues of the soul: "Know from where you came, where you are going, and before whom you are destined to give a judgment and accounting." We speak of the soul's life origins as "a very part of G-d above," of the "World to Come" to which it is propelled by the good deeds of a virtuous life, and of the day it will merit to give "a judgment and accounting" before the Source from which it came and to which it shall return.
And then there is the tzaddik, the perfectly righteous individual. To the tzaddik we don't speak of the lowliness of the body, for the tzaddik's body is refined and rarified, as holy, perhaps even holier, than his soul. Nor do we speak to the tzaddik about his soul -- the tzaddik doesn't care about his soul. He's not interested in spiritual development. He's not interested in the World to Come. All he desires is to lose himself within the all-embracing reality of G-d, like a tiny candle-flame absorbed and nullified within a great fire.
Still, the tzaddik, too, can "come to the hands of transgression." The tzaddik, too, can sin -- not in forgetting about G-d, but in forgetting about the world. The tzaddik may backslide to the pre-Sinai reality, when there were only two things -- only G-d and man, and their quest for each other.
So the tzaddik is admonished: "Reflect upon three things." Remember that Shabbat morning at Sinai when G-d descended upon the mountain and decreed that the world shall henceforth be made real. Remember the day on which G-d decreed that your purpose in life is not to lose yourself within Him, but to bring Him into the world and uplift the world to Him.