After Satan occupied the principled world which God had created, Satan began to bring about the non-principled world against God's will. Therefore, God separated Cain from Abel before He began to work His providence. Cain, as the first-born son., was to represent Satan's side and Abel, the second-born, was to represent God's side.

Each was now in the position to deal with only one master. In Gen. 4:7 God said to Cain, "Why are you angry and why has your countenance fallen? If you do well, will you not be accepted? And if you do not do well, sin is couching at the door; it's desire is for you but you must master it." This shows that Cain was placed in a position to deal with Satan. When the Israelites fled out of Egypt, God smote not only all the first-born of the Egyptians but also of their cattle (Ex. 12:29). Also, God loved the second son Jacob and hated the first son Esau while they were still in their mother's womb (Gen. 25:23). And in the case of Jacob's blessing of his grandsons, Ephraim and Manasseh, he blessed them by crossing his hands to lay the right hand on the head of Ephraim, the second son (Gen. 48:14). These are all examples of how God placed every second-born child in the favored position.