To understand how Jesus could pay for all of our sins past, present, and future we first need to understand what sin is. According to 1 John 4:3, sin is breaking the law of God.  So, sin deals with the Law, with what is legal.  In the famous prayer where Jesus instructed the disciples to pray by saying “Our Father who is in heaven, Holy is Your name…” Jesus speaks of both sin and debt. In the first account of the prayer in Matthew 6:12, Jesus says “and forgive us our debts.” In the second account in Luke 11:4, Jesus says “and forgive us our sins.” So, we can see that Jesus equates sin with debt.  In this case, legal debt.

This is important because legal debts can be transferred. If you owed a bill at a department store, I could go into that store and pay your bill.  In the same way that one person can pay the debt of another, Jesus paid our sin debt on the cross. Theologically speaking we call this imputation. To impute means to reckoned to another’s account. Our sins were imputed to Christ on the cross.  That is, they were reckoned to his account.

• 1 Peter 2:24, “and He Himself bore our sins in His body on the cross, so that we might die to sin and live to righteousness; for by His wounds you were healed.”

We can see that he bore our sins. That is, the legal debt of our sins was taken by Jesus upon himself.  This why it says…

2 Corinthians 5:21, “He made Him who knew no sin to be sin on our behalf, so that we might become the righteousness of God in Him.”

Now we can better answer the question. Since God knows all things (1 John 3:20), everyone’s sin is known by God. In other words, because God knows everything, he necessarily knows every sin that everybody will ever commit. Because our sins are against God, since we break his law, he has a record of all of our sins in the past, present, and future. And since legal debts can be transferred (and sin is a legal debt) God transfers all of our sin debt to Christ on the cross.  Whether or not it is future or past from our perspective is irrelevant to God who indwells all time simultaneously.

Conclusion

So, that is how Jesus is able to pay for all of our sins past, present, and future. Since God is not bound by time, or should we say not restricted by time, all sins that we commit are known by God. Since sin is a legal debt and legal debts can be transferred, then all of our sin debt was transferred to Christ on the cross.