The first reading tells us how God made his covenant with Abraham in 1800 B.C. back when Abraham did not know how to read and write. For the formal ceremony of agreeing to the covenant God let Abraham make the preparations in the only way Abraham knew such things could be done.
Back then there were no governments or formal laws, there were only wandering tribes with their members being completely obedient to their leaders. When it was necessary for two wandering tribes to reach an agreement for sharing grassland or water rights they prepared for a ceremony by digging a three-foot trench across a field between tribes squatting on opposite sides of that field. Then, they would slice down the middle a three-year-old heifer, a she goat, and a ram; placing the halves opposite each other at different stretches of the ditch.
At the same moment the leader of each tribe would step down into his end of the ditch, then walk toward the other, saying, “If I or any of my men interfere with your rights let me be cut in two like this heifer, she goat, and ram.”
(I have read that up to the present when two nations make a covenant the technical language speaks of their “cutting” a covenant.)
In our Mass reading Abraham made all the preparations, then he sat down, waiting, at his end of the ditch. As evening approached a sleep came over Abraham. (It was the same sleep that came over Adam when God removed his rib to form Eve.) Through the darkness Abraham saw God’s torch approaching from the far side of the ditch, touching the halves of the ram, goat, and heifer as it came.
This story assures us that God meets with every one of us on his or her level. He takes an easy, straight-forward way of coming to terms even with mentally deranged people and with infants.