What does Genesis 15:17 mean?

After God completes His prophecy about Abram's descendants, He returns to the covenant ritual that began with Abram dividing and arranging the halves of the animals God had instructed him to bring (Genesis 15:9). Now the sun goes down, and God completes the ritual. Whether Abram is now awake and sees it with his own physical eyes, or sees this event in his vision or dream, we don't know for sure. Either way, what Abram sees is remarkable. In the dark, two items move between the halves of the animals. One is a smoking fire pot, something that served as an oven in Abram's day. The other is a flaming torch.

In the narrative itself, we're not told what these two items represent. However, fire is often associated with both God's judgment and His holiness. In addition, these elements of smoke, fire, and the various kinds of animals later used for sacrifice under the Law point to God's future relationship with Israel.

Finally, in moving between the two halves of the animals, God is apparently finalizing the agreement between Himself and His people through Abram. This aspect, in particular, is important for its symbolism. Scholars suggest that this ritual—passing between the halves of sacrificed animals—was meant to imply a binding oath on those who participated. By walking between the animals, the person was accepting that same destruction if they broke their end of the bargain. Pointedly, note that Abram does not pass between the halves—only God does, via the symbolism of the pot and flame. The promise God has made here is entirely dependent on His will and His work.

Abram had begun this part of the conversation by asking the Lord how he would know if God would keep His promise to give Abram and his descendants the land of Canaan. Abram's dramatic experience of God's answer in performing this covenant ritual would surely have made a lifelong impression on him.