What did God use to confirm His promise to Abraham?

The confirmation of God's promise to Abraham through a flaming torch and a smoking firepot is recorded in Genesis 15. God had promised Abraham descendants as numerous as the stars and a land for his offspring. Abraham asked, "O Lord God, how am I to know that I shall possess it?" (Genesis 15:8).

God instructed Abraham to bring a heifer, a goat, a ram, a turtledove, and a young pigeon. Abraham cut the larger animals in half and arranged the pieces opposite each other. As the sun set and deep darkness fell, a smoking firepot and a flaming torch passed between the divided pieces (Genesis 15:17). This was a covenant-ratification ceremony: in the ancient Near East, parties to a covenant would walk between the halves of slaughtered animals, symbolising their commitment. Remarkably, only God (represented by the fire and smoke) passed between the pieces, making this a unilateral, unconditional promise.

A burning bush is associated with God's call to Moses at Sinai (Exodus 3), not with Abraham. A rainbow was the sign of God's covenant with Noah after the flood (Genesis 9:13). Thunder and lightning accompanied the giving of the Law at Mount Sinai (Exodus 19:16). The specific sign given to Abraham was the flaming torch and smoking firepot.