And when the birds of prey came down upon the carcasses, Abram drove them away.
Read Chapter 15
Augustine of Hippo
The fowls coming down on the divided carcasses represent nothing good but [rather] the spirits of this air, seeking some food for themselves in the division of carnal people. But that Abraham sat down with them signifies that even amid these divisions of the carnal, true believers shall persevere to the end. With the going down of the sun great fear fell upon Abraham and a horror of great darkness. This signifies that about the end of this world believers shall be in great perturbation and tribulation, of which the Lord said in the Gospel, “For then shall be great tribulation, such as was not from the beginning.”