Genesis 15:10

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.

Cross-reference

In Jeremiah 34:18, the same covenant-cutting ritual appears — men cut a calf in two and pass between the pieces, mirroring Abram's ceremony exactly.

In Leviticus 1:17, birds are torn by the wings but not cut in two — contrasting with Abram's practice here of not dividing the birds at all.