Genesis 15:9

Take me. heifer of three years old.

As Noah in the covenant entered into between him and the Lord, stood forth as the representative of the human race; as Abraham, in the "covenant of Christ," which is recorded in Genesis 12:1-5, stood forth as the representative of all who are saved through Christ; so here he stands as the representative of his seed according to the flesh who should possess the land of Canaan. The sacrifices offered are, therefore, the legal sacrifices of the Jewish law. It is worthy of remark that every animal allowed or commanded to be offered under the Mosaic law is to be found in the list. It seems as though while God was ratifying. charter for the possession of this land by his seed that he gave to Abraham an epitome of that law and its sacrifices which were to be fully given through Moses and observed by his descendants. The animals chosen were of the class that constituted Abraham's wealth and were three years old, matured, but not decrepit, in the prime of life, as near perfect in age as they were required to be in other features.