What the Bible says about Burning Torch as Symbol
(From Forerunner Commentary)
Genesis 15:10 and 17 show us a small portion of the ancient practice of making serious covenants. Those making the covenant prepared a sacrifice by dividing animals or fowl in two, then both parties passed between the divided carcasses. This symbolized the seriousness of their intentions in that the divided carcasses represented what would happen to them if they did not keep their oath! They placed their lives at risk. The carcasses were then burned, symbolizing their acceptance.
The smoking oven and burning torch symbolize God. In many instances in the Bible, God represents Himself through the image of fire (i.e., the burning bush and the pillar of fire). The sacrifice in Genesis 15 is interesting in that only God passes between the divided carcasses because, in reality, this is an oath of only one party, God, to keep His promise. In this specific case, Abraham has agreed to nothing, but God has bound Himself with utmost seriousness to meet the requirements of His promise in full. This promise will be fulfilled only because of God's character and grace.
The 14th thus signifies the ratification of the promise by sacrifice, and the 15th, what it accomplishes by providing visible evidence of God's faithfulness (e.g., the Israelites go free).
John W. Ritenbaugh
Countdown to Pentecost 2001