To confirm His promises to Abraham regarding the Promised Land, God made a covenant with him. In Genesis 15:9-17, He asks Abraham to cut some animals in two, and then He passes a firepot and a torch among the pieces.
So the Lord said to him, “Bring me a heifer, a goat and a ram, each three years old, along with a dove and a young pigeon.” Abram brought all these to him, cut them in two and arranged the halves opposite each other;... As the sun was setting, Abram fell into a deep sleep, and a thick and dreadful darkness came over him.... When the sun had set and darkness had fallen, a smoking firepot with a blazing torch appeared and passed between the pieces. (Genesis 15:9-17)
This may seem strange at first, but this was a common practice at that time for making a covenant. Those who were making the promises would say something like this: "As this calf is cut in pieces, so may we be cut in pieces if we do not keep the promises of this covenant." It was a way of making their commitment very serious and legally binding.
Notice how this is confirmed in Jeremiah 34:18-20:
The men who have violated my covenant and have not fulfilled the terms of the covenant they made before me, I will treat like the calf they cut in two and then walked between its pieces. The leaders of Judah and Jerusalem, the court officials, the priests and all the people of the land who walked between the pieces of the calf, I will hand over to their enemies who seek their lives. Their dead bodies will become food for the birds of the air and the beasts of the earth. (Jeremiah 34:18-20)
In other words, both God and Abraham were making an oath that they would be destroyed just like the animals if they did not keep their part of the covenant.
