By Kevin Gyllenberg
The Abrahamic covenant is found in Genesis 15:9-15:18.
In it, God told Abraham to take animals:
The animals, he was to kill, cut the carcases in two, put one on each side, thus forming a kind of lane or avenue, of blood between these divided bodies.
And then, when it was dark, a supernatural fire passed down between those pieces, Abraham did not go between them, but this supernatural fire and smoke representing the presence of the living God went between these pieces.
And we are told "On that day the Lord cut a covenant with Abraham" - "Saying to your descendants, I give this land, from the river of Egypt to the great river the river Euphrates."
It was a custom called a covenant with a self implicating oath. You took the animal, you divided it in two, and you and your contracting friend, the other party, would walk between these divided halves. And you promised to each other, and said, if I break my word, may it be done to me as I have done unto this animal, and more also, in the name of the gods.
Ruth 1:16-17 used the formula of words normal in this type of covenant when she spoke to Naomi. It was the formula of the self-imprecatory covenant.
"The Lord do so to me, and more also, if" literally even death parts me from you. You find that being a monotheist, she swore in the name of the Lord, the true God.
Jezebel was a pagan, and so she said to Elijah in 1Kings:19:2."So let the gods do to me, and more also, if I make not thy life as the life of one of them by to morrow about this time. "
Now, God made this covenant with Abraham.
Abraham did not pass between those divided animals.
God did so and God did so alone, with fire and smoke, the symbol of the divine presence.
Thus, God's oath to him on that day was irrevocable and did not depend upon the obedience of Abraham, but only upon the faithfulness of God.