God’s rescue plan for fallen man existed before the foundation of the world (Ephesians 1:4), because in giving man freedom God not only took the Fall into account, but even foresaw it. In principle, God could have accomplished salvation through the Lord Jesus immediately after the Fall or only at the end of world history; all that matters is that it happens once (Hebrews 9:28). In the first case the price of sin would already have been paid in advance; in the second case it would be retroactive. We also know both by commercial events: prepayment and post-payment. God in His wisdom has determined the “optimum time”. With this in mind, Galatians (4:4) says: “When the fullness of time had come, God sent his Son.” People who lived before Jesus’ coming and who followed God’s instructions for salvation at that time are also through the sacrifice of Calvary saved as those who were born after him and accepted the gospel (Heb 9:15). The temporal aspect of the saving event that already happened for us is expressed in Romans 5:8: “God demonstrates his love toward us, in that while we were yet sinners, Christ died for us.”
Commandments did not exist in the time of Abraham or Job. These men acted according to their conscience and trusted in God. He considered this to be righteousness (Romans 4:3). In David’s time, the Sinai commandments had been in place for a long time. They were the standard for being justified before God; sins were abolished through animal sacrifice. However, the sacrificed animals could not erase sin (Hebrews 10:4); they were merely a hint of the coming sacrifice in Jesus. That is why he is also called “the Lamb of God, who takes away the sin of the world” (John 1:29). Only through him was the debt finally paid. We live in the time of the sacrifice already fulfilled. With this, the shadow images (animal sacrifices) are eliminated and we receive forgiveness based on the sacrifice already made.