This is the context.
7 And he said to him, “I am the Lord who brought you out from Ur of the Chaldeans to give you this land to possess.” 8 But he said, “O Lord God, how am I to know that I shall possess it?” 9 He said to him, “Bring me a heifer three years old, a female goat three years old, a ram three years old, a turtledove, and a young pigeon.” 10 And he brought him all these, cut them in half, and laid each half over against the other. But he did not cut the birds in half. 11 And when birds of prey came down on the carcasses, Abram drove them away.
12 As the sun was going down, a deep sleep fell on Abram. And behold, dreadful and great darkness fell upon him. 13 Then the Lord said to Abram, “Know for certain that your offspring will be sojourners in a land that is not theirs and will be servants there, and they will be afflicted for four hundred years. 14 But I will bring judgment on the nation that they serve, and afterward they shall come out with great possessions. 15 As for you, you shall go to your fathers in peace; you shall be buried in a good old age. 16 And they shall come back here in the fourth generation, for the iniquity of the Amorites is not yet complete.”
17 When the sun had gone down and it was dark, behold, a smoking fire pot and a flaming torch passed between these pieces. 18 On that day the Lord made a covenant with Abram, saying, “To your offspring I give this land, from the river of Egypt to the great river, the river Euphrates,19 the land of the Kenites, the Kenizzites, the Kadmonites, 20 the Hittites, the Perizzites, the Rephaim, 21 the Amorites, the Canaanites, the Girgashites and the Jebusites.” (Genesis 15 7-20 ESV)
The actual format of the covenant appears to be something common to several Ancient Near East cultures. There is a survey of the ANE source materials by G.F. Hasel “The Meaning of the Animal Rite in Genesis 15” in JSOT 19 (1981) pp. 61-78 which links the ceremony to treaty ratification ceremonies recorded at Alalakh.
At Alalakh, the defeated Abban vows the city of Alalakh to his new master Yarimlim, by cutting the neck of a sheep:
“Abban placed himself under oath to Yarimlim and had cut the neck of a sheep (saying): ‘(Let me so die) if I take back that which I gave thee” (Victor P. Hamilton Genesis Chapters 1-17, NICOT 1990, p.376)
A contemporary Hittite military text at Mari shows the example of taking a curse oath when walking between the pieces of a sacrifice:
“Should they ever be defeated, “they perform a ritual behind the river, as follows: they divide in half a man, a goat, a puppy, and a little pig; they place half to the right and half to the left, and in front they make a gate of wood and in front of the gate they light fires to the right and to the left, and the troops walk on the path between them…” (RHR 137, 1950, cited in Hamilton, )
To this there is also a response by G.J. Wenham “The Symbolism of the Animal Rite in Genesis 15: a Response to G.F. Hasel” (February 1, 1982) who notes that the animals selected – a heifer, a female goat, a ram, a turtledove, and a young pigeon – are animal types which show that the covenant is more about blessing than cursing. Though the format of passing through sacrifice does mean taking on the burden of a curse, and occurs later for a solemn oath of officials in Ancient Greece (Plato Laws 753d).
Note also that a reference to the judgment on the person not keeping such a treaty is found in Jeremiah:
18 And the men who transgressed my covenant and did not keep the terms of the covenant that they made before me, I will make them like the calf that they cut in two and passed between its parts— (Jeremiah 34:18 ESV)
There is certainly some context, or comparison with, the Hittite examples. The point here however is that it is not , as you would expect, Abraham who passes through the pieces, but instead it is God himself, passing in a theophany. It is God who places himself in covenant.
From the context it can be seen that though said to Abraham this covenant looks forward to the time of the Exodus and Israel in Egypt. Therefore the pot of fire and torch are probably intended to foreshadow the pillar of cloud and pillar of fire in Exodus 13:21.