And he took unto him all these, and divided them in the midst, and laid each piece one against another: but the birds divided he not.
Read Chapter 15
Augustine of Hippo
And it is said, “But the birds divided he not,” because carnal people are divided among themselves. But those who are spiritual are not divided at all, whether they seclude themselves from the busy conversation of humankind, like the turtledove, or dwell among them, like the pigeon. For both birds are simple and harmless, signifying that even in the Israelite people, to which that land was to be given, there would be individuals who were children of the promise and heirs of the kingdom that is to remain in eternal felicity.
Now notice carefully Abraham is said to have divided the three animals into two parts and to have placed them one against the other. “The birds,” says Scripture, “he did not cut in two.” Why is this, brothers? Because in the church catholic, carnal people are divided but spiritual people are not. And, as Scripture says, they are separated one against the other. Why are carnal people divided and set against each other? Because all wicked lovers of the world do not cease to have divisions and scandals among each other. For this reason they are divided, since they are opposed to one another. However, the birds, that is, spiritual souls, are not divided. Why not? Because they have “one heart and one soul in the Lord.” To will and not to will is all one thing to them. Surely the turtledoves and pigeons that we mentioned above are like these souls. In the turtledove chastity is represented, and in the pigeon, simplicity. All Godfearing people in the church catholic clearly are chaste and sim...