Genesis 15:9-17

The LORD told 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.” So Abram presented all these to him and killed them. Then he cut each animal down the middle and laid the halves side by side; he did not, however, cut the birds in half. Some vultures swooped down to eat the carcasses, but Abram chased them away. As the sun was going down, Abram fell into a deep sleep, and a terrifying darkness came down over him. Then the LORD said to Abram, “You can be sure that your descendants will be strangers in a foreign land, where they will be oppressed as slaves for 400 years. But I will punish the nation that enslaves them, and in the end they will come away with great wealth. (As for you, you will die in peace and be buried at a ripe old age.) After four generations your descendants will return here to this land, for the sins of the Amorites do not yet warrant their destruction.” After the sun went down and darkness fell, Abram saw a smoking firepot and a flaming torch pass between the halves of the carcasses.