Behold a smoking furnace This signified the affliction of his seed in Egypt: they were there in the furnace of affliction, and labouring in the very fire. They were there in the smoke, their eyes darkened that they could not see to the end of their troubles. And a burning lamp This speaks comfort in this affliction: and this God showed Abram at the same time with the smoking furnace. The lamp notes direction in the smoke; God's word was their lamp, a light shining in a dark place. Perhaps, too, this burning lamp prefigured the pillar of a cloud and fire which led them out of Egypt. The “passing of these between the pieces” was the confirming of the covenant God now made with him.
Related Commentaries of Genesis 15:17
Genesis 15:17
17 And it came to pass, that, when the sun went down, and it was dark, behold a smoking furnace, and a burninga lamp that passed between those pieces.