Genesis 15:6-14

And Abram believed the LORD, and the LORD counted him as righteous because of his faith. Then the LORD told him, “I am the LORD who brought you out of Ur of the Chaldeans to give you this land as your possession.” But Abram replied, “O Sovereign LORD, how can I be sure that I will actually possess it?” 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.