Recently I read someone explaining how he was no longer a Christian because he did not believe that it was just of God punish even a willing victim to pay for our sin. At the first glance it seems like this man is correct. How could a good God punish one person for another's sin? It seems so unfair. But taking a closer look at a few key things from Scripture reveals how wrong this is.
First, understanding who God is. God is triune. He is three persons yet one God. The three persons of God, the Father, the Son, and the Holy Spirit, are one such that seeing one of them act is the same as seeing the others act, thus Jesus says to His disciples that by seeing Him they had seen the Father. (John 14:9) The Trinity is pictured in multiple places, the best of which is when Jesus is baptized. At that time the Father proclaimed that Jesus is His Son and at the same time the Holy Spirit descends in the form of a dove. (Luke 3:21-22) The Trinity is like a marriage – the relationship between a man and his wife is one of selfless love, and so is God's relationship to Himself. So Jesus when He is faced with the cross goes willingly as He seeks to do His Father's will. (Luke 22:39-46 and Hebrews 12:2)
Second, the definition of sin. Sin is not just bad or wrong things that a person does, but offenses he commits against God. My sins (i.e., lying, lust, hatred, or pride) are all ultimately crimes against the Holy God who made me, and not crimes against my neighbor, even when they are also offenses against my neighbor. (Psalm 51:4)
Third, what forgiveness is. Forgiveness is best illustrated in the parable that Jesus told about the man who owed his king ten thousand talents. (Matthew 18:23-35) In that parable, Jesus says the king is settling all his accounts, and he calls in a servant who owes him the tremendous sum of ten thousand talents. A talent is a weight of gold that was worth approximately twenty years of a laborer's wages. (Ibid.) This is 200,000 years of wages, or about 9 trillion dollars today in 2012. Clearly this man is going to have a hard time paying this debt. Actually I think that Jesus point here is that the man is not going to be able to pay it back. The man however pleads with the king asking for mercy because he says he will pay it back. However the king gives him more than he asks for and tells him that he will forgive the debt. The king gives up whatever he could have done with that money by forgiving the debt. He says in essence, “Whatever project I am working on that needs that money, it is not as important to me as you are.” Forgiveness is saying to someone, “I will cancel the debt that you owe to me.”
But the debt still has to be paid by someone. In the parable the king pays it. Jesus says that the kingdom of Heaven, God's kingdom, is like that parable. The Father has given all authority to the Son, Jesus. (Matthew 28:18 Jesus has been exalted by being given the seat at the Father's right hand. He has been made king over all creation and will come again to judge the world. (Acts 2:33-36 and Matthew 25:31-46) When He returns again He will be the one who publicly pardons the sins of His people. Jesus paid the debts of those who trust in Him, though ultimately the debts are to Himself. (Galations 3:13)
This is not the same as me forcing my child to pay debts owed to me by our neighbor, it is more like my child inheriting my estate after I am gone (remember that Jesus, the Son, is the King now) and in his good will forgiving a debtor who had owed me money. There is nothing unjust about that at all.