The first seven chapters of the book of Leviticus are devoted to the laws of the korbanot (“offerings”  ). When the Beit HaMikdash (Holy Temple) stood in Jerusalem, the primary mode of man’s worship of G-d was the korban: an animal and/or meal offering brought in fulfillment of a vow, to atone for a wrongdoing, to express gratitude, or simply as a gift to G-d. There were also daily offerings and special Shabbat and Festival offerings brought by the community as a whole. Every significant occasion on the communal calendar, every event and experience in the individual’s life—each had its expression in a korban, an offering to G-d.
The korbanot fall under three general categories: shelamim (“peace offering”), chattat (“sin offering”) and olah (“ascent offering”). 
The shelamim offering was brought as a donation to G-d or to celebrate a joyous occasion.  Parts of it were burned on the altar  and specified portions were given to the kohanim (priests),  but the bulk of the korban was eaten—under special conditions of ritual purity—by the person or persons making the offering. Indeed, one of the reasons for the name shelamim—“peace offering”—is that there is something in it for everyone: G-d receives His part, the kohanim theirs, and the owner gets to enjoy the very gift he consecrated to G-d.
The chattat offering (which also includes a related category, the asham or “guilt” offering  ) was brought in order to atone for a person’s transgression of a divine command  or to achieve the reparation of certain negative states.  These were eaten by the kohanim  after the prescribed parts were burned upon the altar.
The olah, however, was a pure offering, serving no function other than to express its offerer’s commitment to G-d. It was wholly consumed by the fire that burned upon the altar.
Abraham, the first Jew, lived one hundred and seventy-five years.  A full account of everything he said and did would fill many volumes. The Torah, however, chooses to relate to us the details of selected events, devoting a few thousand words to the story of his life. The same is true of Sarah, Isaac, Rebecca, Jacob, Rachel, Moses, David and the other “heroes” of the Torah’s narrative: what we are given is, at most, a sampling of their personal histories. Certain seemingly minor occurrences are described at length, while there are “blank” years and even decades in the accounts of their lives. 
For the Torah is not a book of biography, or even history; it is, as its name implies,  a lawbook, a book of instruction. Many of its chapters (particularly in the books of Leviticus and Numbers) are indeed straight recitations of the laws of life. But also the Torah’s “stories” are strictly instructive, their every detail an eternal lesson in how to live our lives. As Nachmanides writes in his commentary on Genesis 12:6:
“Understand this rule regarding all following chapters [of the Torah]… Everything that happened to the Patriarchs is a signpost for their children. This is why the Torah elaborates on its account of their journeys, their well-digging and other events which one might think superfluous and insignificant: these all come to instruct the future. When something happens to one of the three Patriarchs, one understands from it what is decreed to occur to his descendants.”
One of the first things the Torah describes Abraham doing is building a series of altars to G-d at various locations in the Holy Land. The first altar erected by Abraham was in “the vicinity of Shechem,” where G-d had appeared to him and informed him that:
“To your descendants I will give this land.” 
The altar, explains Rashi,  was to express Abraham’s gratitude to G-d for:
“…the promise of children (Abraham was childless at the time) and the promise of the land.” 
(Regarding each of the three altars, the Torah emphasizes that “he built there an altar,” implying that the reason for the altar’s construction relates to an event that took place at that locality.)
Abraham built a second altar between “Beth-El to the west and Ai to the east.”  This was the site where, centuries later, the people of Israel suffered defeat in battle as a result of Achan’s transgression of the divine command not to take anything from the booty of the conquered city of Jericho.  Abraham, says Rashi:
“…prophesied that his descendants were destined to stumble there as a result of Achan’s sin, and he prayed there for them.” 
The third of Abraham’s altars was built upon his arrival in “the Plain of Mamre, which is in Hebron,”  where Abraham was to live for many years. Regarding this altar, however, Rashi does not give any reason for its construction, although there is no shortage of events of great significance in Jewish history connected with the city of Hebron. The verse states, simply, that “he built there an altar to G-d,” and, unlike the first two altars, Rashi feels no need for any further explanation. 
The Holy Meal
With his three altars, Abraham was establishing the precedents for three basic elements in our relationship with G-d. His first altar expressed the truth that we turn to G-d because we need Him. Our requests and expectations from G-d are as varied as life itself, but whether we are seeking material support or spiritual fulfillment, the underlying premise is the same: we are involved with G-d because of what we get out of the relationship.
This is the element represented by the shelamim category of korbanot. The shelamim was an offering to G-d, yet its primary effect was the nourishment of the one making the offering. With the exception of the relatively small contributions made to the altar, the offering was “given back”—“from the Supernal Table,” as the Talmud puts it—to its original owners (and the kohanim). 
To the spiritually mature individual, this might seem a shallow and selfish conception of our relationship with G-d. But the recognition that everything we are and everything we have is a gift from Above is elementary to every level of spiritual sensibility, including the most sophisticated and altruistic. A person who devotes himself utterly to the service of G-d but does not regard his daily bread as something he requires from G-d, lacks a most basic understanding of his relationship with his Creator. 
After building the altar at Shechem in gratitude for G-d’s blessing to him, Abraham built the altar near Ai to serve as the “signpost” and prototype for the second aspect of our bond with G-d: our recognition of our own deficiency in the face of His perfection. Our recognition that we are all “guilty” in our relationship with Him, whether by overt transgression of His will or by the more subtle meaning of chattat, which is “lack” and “failing.” On this level—the level represented by the korban chattat—the purpose of our service to G-d is to atone for our deficiencies, to elevate ourselves to worthiness of connection with Him.
The Third Altar
The common denominator between the shelamim and chattat offering is that both are the means of achieving something for man, whether it is the attainment of a material or spiritual gift from G-d, or the elimination of a deficiency. This is alluded to by the fact that both the shelamim and chattat were given for human consumption—the former by the lay Jew, connoting its relationship to the procurement of (even) material needs, and the latter by the consecrated kohen, indicating that its objective is a loftier and more subtle “gain.” The olah, however, was an offering in the ultimate sense of the word: something that man gives to G-d for no reason other than to give to G-d.
With his third altar, Abraham established the precedent for the third and ultimate level of relationship with G-d: man’s self-abnegation to the divine will. On this level, man does not serve G-d because G-d is the source of all of life’s blessings, nor, even, to atone for his own failings and shortcomings, but simply to serve his Creator, without any purpose or motive other than causing Him pleasure. 
Abraham built his third altar at Hebron, a place that embodies the ultimate connection between G-d and Israel. Here are buried Abraham, Isaac and Jacob, who are the three cornerstones of our bond with G-d.  Our sages tell us that all prayers ascend to Heaven via Hebron,  and the city’s very name means “bond” and “connection.” Hebron is also the place where King David was first crowned sovereign of Israel—a sovereignty whose culmination is the kingship of Moshiach, who will effect the ultimate bond between man and G-d.
Based on an address by the Rebbe, Cheshvan 7, 5746 (October 22, 1985)
 . The word korban derives from karov, which means “close”; a korban is something “brought close” (i.e., offered up) to G-d, as well as something that brings the person who offers it close to G-d.
 . Midrash Tadshe (also called “Baraita of Rabbi Pinchas ben Yair”), ch. 12; Sefer Raziel HaMalach. Maimonides (Mishneh Torah, Laws of the Procedures of the Offerings, 1:2) speaks of four categories—olah, chattat, asham and shelamim; but the chattat and the asham (“guilt offering”) serve a similar function—the reparation of a negative state or situation.
[Cf. Talmud, Ketubot 10b: “The altar removes evil decrees, brings nourishment to the world, enhances the love between G-d and Israel, and atones for sins.” Here, too, we have four functions, corresponding to the four types of offerings brought upon the altar, which (as the Talmud itself points out) can be generalized as three: a) for the benefit of man (“brings nourishment”; shelamim); b) the counteraction of negative things (“atones for sins” and “removes decrees”; chattat and asham); and c) an altruistic offering to G-d (“enhances the love between G-d and Israel”; olah).]
 . Such as the shalmei simchah, brought by all who made the thrice-yearly pilgrimage to Jerusalem to celebrate the festivals of Passover, Shavuot and Sukkot, or the korban todah, brought in thanksgiving for a personal salvation.
 . Specified veins of fat (called chalavim and eimurim) in an animal offering, and a fistful (kometz) of dough or bread from the meal offerings.
 . The breast and the right hind leg in an animal offering (and selected loaves from the accompanying meal offering).
 . See note 2 above.
 . The standard chattat atoned for unintentional transgressions. In certain cases, the Torah prescribes a chattat or asham for an intentional transgression.
 . E.g. the chattat and asham offerings brought by a healed metzora(leper) or a nazirite who had become ritually impure.
 . With the exception of the five “burnt chattaot” which were wholly burned upon the altar (see Mishneh Torah, loc. cit., 1:16-17).
 . Genesis 25:7.
 . For example, the Torah tells us virtually nothing about Abraham’s first seventy five years, and nothing at all about what Moses’ life between the ages of twenty and eighty.
 . The word torah means “law” and “instruction.”
 . Genesis 12:6-7.
 . Rabbi Shlomo Yitzchaki (1040-1105), author of the most basic commentary on Torah.
 . Rashi, ibid.
 . Genesis 12:8.
 . As related in Joshua 7.
 . Rashi, Genesis, ibid.
 . Genesis 13:18.
 . This is in contrast with the Midrashic sources (Midrash Rabbah, Bereishit 39:24; Midrash HaGadol on this verse) that suggest various reasons for the altar built at Hebron. Rashi, however, sees the very point of this altar as not having any reason or objective, as will be explained.
 . Talmud, Beitzah 21a (see Rashi there, s.v. kohanim mishulchan gavo’ah); ibid., Kiddushin 52b. This is why the meat and bread of the korban were “holy,” and could be eaten only in the holy city of Jerusalem and under conditions of ritual purity.
 . By the same token, the most basic function of prayer—which today fills the role of the korbanot in our service of G-d—is that we request our daily needs from G-d, thereby acknowledging that our relationship with Him is not limited to our spiritual life but also embraces the most rudimentary aspects of our being. Indeed, the gist of the most solemn part of our daily prayers—the amidah or shemoneh esrei—is a series of requests for sustenance, health, understanding, atonement and redemption (see A Glass of Milk, WIR, vol. V, no. 50; The Legacy of Cain, vol. VII, no. 5).
 . More specifically, every korban includes these three elements of relationship with G-d: benefit to man, atonement, and selfless sacrifice to G-d. Every korban, including the shelamim and the olah, effected atonement for the one who brought it when its blood was sprinkled upon the altar (Torat Kohanim on Leviticus 1:4; Talmud, Zevachim 6a). There was nourishment for man (i.e., for the owner and/or the kohen) in every korban—even the completely burned olah was first skinned and its hide given to the kohen (Leviticus 7:8). And something of each korban—from the almost completely eaten shelamim to the entirely burned olah—was consumed by the divine fire that burned upon the altar.
In other words, there is an element of self-sacrifice even in the most self-oriented relationship with G-d, and there is benefit to man (both in terms of nurture and atonement) also in his most selfless service.
 . See Nachmanides’ commentary on Genesis 12:6, quoted above; Tanya, ch. 18.
 . Yalkut Reuveni on Genesis 23:9. See Likkutei Sichot, vol. XXV, p. 98, note 69.
 . Likkutei Sichot, vol. XXX, pp. 36-43.