What did God require from the early people in order to accept them and be reconciled to them?
God required the early people to do what He asked by bringing a blood sacrifice, and then He would accept them and be reconciled. Abel is the example: he was accepted because he obeyed God's instruction, while Cain rejected and rationalized it, choosing his own way.
Les explains that God had offered restoration and reconciliation if the early people would simply do what He asked: bring a blood sacrifice, and He would accept them. Abel is the example of acceptance because he did what God told him; Cain rejected it, rationalized it, and went his own way. Les notes this pattern continued until, after 2000 years of patience, God turned to one man of faith to create a special race and bring the plan of redemption, which provoked the devil's opposition.