7 Then He said to him, “I am the Lord, who brought you out of Ur of the Chaldeans, to give you this land to inherit it.”
8 And he said, “Lord God, how shall I know that I will inherit it?”
9 So He said to him, “Bring Me a three-year-old heifer, a three-year-old female goat, a three-year-old ram, a turtledove, and a young pigeon.”
10 Then he brought all these to Him and cut them in two, down the middle, and placed each piece opposite the other; but he did not cut the birds in two.
11 And when the vultures came down on the carcasses, Abram drove them away.
12 Now when the sun was going down, a deep sleep fell upon Abram; and behold, horror and great darkness fell upon him.
13 Then He said to Abram: “Know certainly that your descendants will be strangers in a land that is not theirs, and will serve them, and they will afflict them four hundred years.
14 And also the nation whom they serve I will judge; afterward they shall come out with great possessions.
15 Now as for you, you shall go to your fathers in peace; you shall be buried at a good old age.
16 But in the fourth generation they shall return here, for the iniquity of the Amorites is not yet complete.”
17 And it came to pass, when the sun went down and it was dark, that behold, there appeared a smoking oven and a burning torch that passed between those pieces.
18 On the same day the Lord made a covenant with Abram, saying: “To your descendants I have given this land, from the river of Egypt to the great river, the River Euphrates—
19 the Kenites, the Kenezzites, the Kadmonites,
20 the Hittites, the Perizzites, the Rephaim,
21 the Amorites, the Canaanites, the Girgashites, and the Jebusites.”
One each of the five acceptable sacrificial animals (cow, sheep, goat, pigeon, dove) was to be slain by Abram and laid on the altar. The slain animals were placed in two rows, one bird in each, along with a half-portion of each of the other animals. This arrangement was evidently intended to conform to the custom of the day, when a covenant was made between two parties; each would pass between the two rows, as a sign that he was bound by the terms of the contract. The intimation perhaps was that, if he broke it, the substitutionary death of the animals would no longer be efficacious and he himself (or possibly his cattle) would be subject to death. …
After Abram made the preparations, however, nothing happened during the rest of the day, and finally the sun went down. The delay possibly symbolized the fact that, although God’s covenant would be sure, its accomplishment would take a long time. In the first place, Abram himself would have to wait many years for the promised seed. Even then, it would still be many long centuries before the seed would become a great nation and possess the promised land, and many millennia before the ultimate fulfillment would take place, with all nations being blessed through the nation of Abram’s seed.
During the wait, as could be expected, Abram had to drive off the birds of prey that dried to devour the carcasses. This experience, no doubt symbolized the attempts of Satan to thwart the plans of God. — Morris, page 326
Up to this day in Abraham’s life, God was wont to say to him, “I will give thee this land,” but from the hour of this blood-sealed covenant, He says, “I have given thee this land;” for promises based upon the precious blood of Christ are so absolutely sure that faith can claim them as already possessed. — Williams, page 20.
The reason for the delay, God said, was that “the iniquity of the Amorites is not yet full.” Just as God delayed the judgment of the Flood for 120 years, so here He waited four hundred years. “God is not willing that any should perish” (2 Peter 3:9).
then, when it was dark, a smoking firepot and a flaming torch, representing God’s presence in the covenantal relation with Abram, passed between the two parts of the sacrifice. Only God passed through, not Abram, denoting an unconditional promise on God’s part, not dependent on Abram’s fulfilling his part of the contract, since he had no such part. It was all of God, in response to Abram’s believing faith. In order for God to keep His covenant, there must first be suffering, with glory then to follow. This is suggested by the furnace and the lamp.
The covenant, already made, is now expounded. The land which God will give Abram is from the Nile to the Euphrates, the land then occupied by Canaanites, represented by the ten tribes named. For a very brief time, under Solomon (1 Kings 8:65) and possibly again under Jeroboam II (2 Kings 14:25), the children of Israel ruled all this territory, as a token of the final and permanent possession they will have in the future. — Morris, page 328.
Having affirmed—and hence, for the moment, assuaged Abram’s doubt about—the promise of an heir, God next affirms the covenant promise of Abram possessing “this land” (i.e., Canaan). Not unexpectedly, this prompts a new expression of doubt on the part of Abram, who responds to God’s affirmation by asking, “How may I know that I shall possess it?”—to which, again, God responds with patience and grace. I this instance, however, since the provision in view is abstract (i.e., the right of possession/ownership) rather than material (such as an heir and descendants), God affirms His promise and assuages Abram’s doubts by condescending to participate in the accepted human convention of covenant “ratification” (i.e., establishing a “binding” agreement), which was for the covenantee to be “bound” to the conditions of the agreement by the blood of a sacrifice—either by walking between the bloody parts, as here, or being sprinkled by the blood, as in Exodus 24:6-8, where both Israel and God (represented by the altar) are sprinkled with the sacrificial blood, both sides having certain conditions to fulfill. In this instance, though God adopts the generally accepted form of ratification, He “tweaks” it to conform to the unconditional nature of His promise to Abram. Thus, while Abram is waiting for God, as the superior party, to pass between the pieces, he falls into a deep sleep (induced by God), during which God passes between the pieces in the form of a smoking oven and a flaming torch—thereby ensuring that the pieces were completely burned up in the process (as in 1 Kings 18:38). Consequently, when Abram awoke, he would have perceived that (1) God had passed between the pieces, and (2) that He had done so in such a way as to prevent Abram from doing so afterward, the point thus being clearly driven home that the only one to whom the covenant is “bound” for its fulfillment is God—i.e., it is unconditional. This is likewise Paul’s point in his comment on this event in Galatians 3:17, in which he clearly states that the Abrahamic covenant was “ratified by God” alone, hence justifying his designation of it as a “promise” (= unconditional covenant) rather than “law” (= conditional covenant). — Wechsler, pages 189-190.