[God] said to [Avram]: "Bring me a three-year-old heifer, a three-year-old she-goat, a three-year-old ram, a turtledove, and a young pigeon." He brought Him all of these, split them down the middle, and laid each half opposite the other, but he did not split the birds. Birds of prey came down on the carcasses and Avram drove them away. As the sun was about to set, a deep sleep fell upon Avram, and, behold, terror and great darkness were falling upon him. He said to Avram, "Know well that your offspring will be foreigners in a land not theirs, and they will enslave them and afflict them for four hundred years. But also the nation whom they will serve, I will judge, and afterwards they will come out with great wealth. And, as for you, you will go to your fathers in peace. You will be buried in good old age. And the fourth generation will return here, because the iniquity of the Emorites is not yet complete." When the sun set and it was dark, there was a smoking furnace and a flaming torch that passed between these pieces. (15:9-17)
This sacrifice in Brit Bein Habetarim was a unique one, and at first glance, seemingly a strange one. But by looking at various contexts, I think we can piece together the purpose and meaning of every element in the story.
1. Why pieces of animals?
(This section is mostly based on this article.)
Note the similarities between Brit Bein Habetarim and the splitting of the Red Sea: 1) both involve a "passage" between "pieces"; 2) the "smoking furnace and a flaming torch passing between pieces" in Brit Bein Habetarim recall the pillars of smoke and fire passing through the split sea. Note also the ceremony in Yirmiyahu 34:8-19, where the people cut a calf in two and walk between its pieces, to symbolize their covenant to free their slaves. Here too, the subject of a "covenant of pieces" was freedom from slavery, as was the splitting of the Red Sea.
It is hard to ignore these connections, and what is left is to work out what they signify. One possibility is as follows. It is often said that in ancient Near East culture the act of walking between pieces symbolize the making of a covenant. Thus Brit Bein Habetarim took the normal form of a covenant - whose subject happened to be redemption from slavery - while the splitting sea signified that the covenant had been fulfilled. Yirmiyahu's covenant involved pieces either incidentally, or else to consciously alluded to Brit Bein Habetarim and indicate that it embodied the same values.
Alternatively, it is possible that the subject of all covenants of pieces was freedom from slavery, with the walking between pieces symbolizing exiting the place of slavery through a gate or doors. In this case, all three ceremonies would have indicated in their appearance what their subjects were.
2. Why these particular animals?
Heifer, goat, ram, and birds are all typical sacrificial animals. But there may also be a symbolism in their number. Brit Bein Habetarim promises that "the fourth generation will return here", and paralleling this, three animals are cut in pieces, while the fourth type of animal is not cut up. This may symbolize that the fourth generation does not undergo the suffering of the previous three generations. Alternatively, it may indicate that the slavery which is the typical subject of "covenants between pieces" does not persist to the fourth generation.
Note also the question of how to translate "meshuleshet". Above, I understood this word to be a property of a single animal (its age). But the word could also be translated as "triple", meaning three of each type of animal. Nevertheless, the same symbolism might work even with this translation, as follows:
Recall that two dates appear in the prophecy here: 400 years as well as 4 generations. These dates are in tension with each other, as normally a generation last far less than 100 years. Perhaps the best resolution of the tension is to say that some individuals leaving Egypt would belong to the fourth generation of exiles, while the bulk would belong to the approximately the tenth generation (assuming the standard 40-year generation, and dividing 400 by 40).[1] Indeed we see that Exodus leaders such as Moshe, Korach, and Nachson belonged to the fourth generation, while Yehoshua belonged to about the 11th generation (Divrei Hayamim Alef 7). Perhaps, in ancient Israelite society, the respect for "elders" meant that the oldest surviving members of a generation would be granted leadership authority by default. So the few survivors of the fourth generation were overrepresented among leaders, while most of the population was of a much later generation. In such a case, a 400 year exile corresponds to the 10th generation, and if so the 9 animals to be cut up correspond to 9 generations of slavery, while the 10th and 11th animals are not cut up as these generations would go free.
3. Why the scavengers?
The distinctive aspect of the prediction in Brit Bein Habetarim - that a long period of suffering occurs before the people goes free - also appears to be reflected in another aspect of the story. "Birds of prey came down on the carcasses and Avram drove them away." Avram performed his sacrifice sometime during the day. But rather than receiving an immediate response (akin to the fire which descended to consume the sacrifice in parshat Shmini), for a long time he was left waiting for a Divine response (perhaps wondering if a response would ever come). In the meantime, was forced to awkwardly shoo the scavenging wildlife off the sacrifices. This wait corresponds to the promised long period of slavery, during which the people would naturally wonder whether God had abandoned them and whether salvation would ever come.
4. Why the negativity?
The beginning of the prophecy - "A deep sleep fell upon Avram, and, behold, terror and great darkness were falling upon him" - is not exactly a positive image, and seems to portend a negative promise, not a positive one. And indeed, much of the promise that was given - the 400 years of servitude - was quite negative. Why? Did Avraham really deserve such negative promises?
Brit Bein Habetarim comes immediately after a heroic action by Avram - he goes to war to rescue a plundered hostage population, defeats a far more powerful enemy, and when greeted publicly upon his return, refuses to take any personal benefit from the spoils. All this is remarkable and merits a great reward from God. But it comes on the heels of a rather different story. Having migrated from Haran to the promised land as commanded by God, his next step was to depart for Egypt in a famine, even at the cost of calling Sarah his sister, and profiting from Pharaoh's attempt to contract an unwittingly adulterous marriage with her. What happened to the Divine promise that he would be blessed for moving to Israel? While one might argue that escaping a famine is justified under something like pikuach nefesh, Ramban (Breishit 12:10) nevertheless criticizes Avram for leaving the land in seeming disregard of the divine promise, and I think the Torah suggests the same message when it describes the consequences of Avram's expedition. Brit Ben Habetarim, which follows shortly after these events, promises Avraham exile to (as it turns out) Egypt, followed by miraculous punishment of Pharaoh, and a wealthy exit - an exact repeat of Avram's trip to Egypt.
Furthermore, it seems that the divine promise of an exile paralleling Avraham's trip was not an arbitrary decision by God, but rather there also exists a causal connection between the two events, as in a sense Avraham's trip led directly to the Egyptian exile. Were it not for Avraham's trip he likely would not have acquired the Egyptian maidservant Hagar, nor would he and Lot have acquired the wealth that led them to split up. Thus, the separations from both Yishmael and Lot were indirectly caused by the trip. This history of separation from unchosen family members likely led Rivkah to assume that Yaakov too was about to be expelled (as Yitzchak favored Esav) - leading Yaakov to steal Esav's blessing, which in turn lead to Yaakov's fleeing, his trick marriage to Leah, the murderous rivalry that emerged between the children of Yaakov's wives, and the sale of Yosef to Egypt, followed by the exile of the whole family. Faced with this history as well as the predictions of Brit Bein Habetarim - both seemingly alluding to Avram's Egypt trip - it is hard not to look at that trip with a critical eye.
So where did Avram stand at the time of Brit Bein Habetarim? On one hand, he had seemingly committed a major sin. On the other hand, he had also just performed feats of remarkable heroism in God's name. I suspect this dual history accounts for the Brit Bein Habetarim. He was given a covenant and promises of fabulous reward for his offspring - but before receiving that reward, the same offspring were condemned to suffer for generations.
5. Why wasn't there negativity beforehand?
Brit Bein Habetarim is not the first event to happen after Avraham's trip to Egypt; several other events occur in between. First Avraham returns to the altar he once built near Beit El, and calls out in the name of God. Then a conflict develops between Avraham and Lot's shepherds, and Lot departs for Sedom. Then God repromises the land to Avraham:
Lift up your eyes and see, from the place you are in, north and south and east and west. For all the land you see I will give you and your offspring forever. I will make your offspring like the dust of the earth - if a man could count the dust of the earth, so too your offspring could be counted. Rise and walk in the land, to its length and breadth, for I will give you it. (13:14-17)
Only then does the war with the four kings start, and after it Brit Bein Habetarim. If Avraham indeed sinned in descending to Egypt and had to be punished for this sin, why wasn't this mentioned right away?
I don't have a definitive answer to this question, but here is one possibility.
We as readers, and of course God as well, can recognize the potential religious issues in Avraham's descent to Egypt. But we are not the only ones. Presumably Avraham himself recognized - following the taking of his wife, his unceremonious expulsion from Egypt, and the loss of his nephew - that something had gone wrong. He may have been uncertain how much moral fault he had in the events - just as the later commentators are uncertain - but it seems likely that in some way he suspected he had failed to meet his normal moral standards, perhaps failed badly.
And he may have concluded that such moral failures have implications for the future as well. Perhaps, after this event, God would no longer want Avraham as His representative in the world, Avraham having failed at the mission God tasked him with. Or perhaps now the mission simply felt too big for Avraham, and he wished to be relieved of it. The easiest thing would have been to follow Lot to Sodom - abandoning his role as a "prince of God among [the inhabitants of the hill country]" (23:6) to be reunited with his nephew, living comfortably along the perennial waterways of Sodom,[2] albeit in proximity to the sinful Sodomite people who would never accept his message.
But God did not want this. Whatever the Divine judgment of Avraham's trip, one imagines that Avraham was still God's best option as a human representative in that generation. And so God had to persuade Avraham that the Divine mission was still worth undertaking. To do that, God gave the effusive promise of 13:14-17. The punishment for Avraham's apparent misjudgment was not removed, but God delayed revealing it, waiting to do so until it would be paired in an unbreakable covenant with an even bigger reward, in Brit Bein Habetarim.
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[1] Alternatively, we might suggest that "generation" here refers to an entire lifetime, which appromiates 100 years. Thus the French word siècle (meaning century) is derived from Latin saeculum (meaning era or world), as the world seen by a cohort of people consists of the 100 or so years of their lifespan. From "saeculum" comes the English word "secular" meaning non-religious (worldly), as well as the term "secular trend" meaning a long-term trend which spans a whole era. The Hebrew "olam" has the same double meaning of "era" and "world".]
[2] The Jordan valley, to which Sodom was apparently adjacent, is described as "fully watered... like the land of Egypt" (13:10), presumably from the waters of the Jordan river.
