9 The Lord told him, "Bring me a three-year-old heifer, a three-year-old female goat, a three-year-old ram, a turtledove, and a young pigeon." 10 So Abram presented all these to him and killed them. Then he cut each animal down the middle and laid the halves side by side; he did not, however, cut the birds in half. 11 Some vultures swooped down to eat the carcasses, but Abram chased them away.
Matthew Henry's Commentary on Genesis 15:9-11
Commentary on Genesis 15:7-11
(Read Genesis 15:7-11)
Assurance was given to Abram of the land of Canaan for an inheritance. God never promises more than he is able to perform, as men often do. Abram did as God commanded him. He divided the beasts in the midst, according to the ceremony used in confirming covenants, Jeremiah 34:18,19. Having prepared according to God's appointment, he set himself to wait for the sign God might give him. A watch must be kept upon our spiritual sacrifices. When vain thoughts, like these fowls, come down upon our sacrifices, we must drive them away, and seek to attend on God without distraction.