When the sun set and it was very dark, there appeared a smoking oven, and a flaming torch that passed between those pieces.
Rashi / Pirkei d’Rabbi Eliezer
English: A smoking furnace and a flaming torch — He hinted to him that the monarchies would descend into Gehinnom. And the torch is the agent of the Shechinah that passed between the pieces.
Supplementary classical material not listed by Torah Temimah under this exact passuk.