Rabbi Joshua said: Abraham took his sword and divided them, each one into two parts, as it is said, "And he took him all these, and he divided them in the midst" (Gen. 15:10). Were it not for the fact that he divided them, the world would not have been able to exist, but because he divided them, he weakened their strength, and he brought each part against its corresponding part, as it is said, "And he laid each half over against the other" (ibid.).
And the young pigeon he left alive, as it is said, "But the bird he divided not" (ibid.). Hence thou mayest learn that there was not any other bird there except a young pigeon. The bird of prey came down upon them || to scatter them and to destroy them. "The bird of prey" is nought else but David, the son of Jesse, who is compared to a "speckled bird of prey," as it is said, "Is mine heritage unto me as a speckled bird of prey?" (Jer. 12:9).