That’s really two questions and we’ll look at the parts separately. First, if God is holy, why does he forgive sin. One must be careful in attributing motives to God, however, there are several things that come to mind which have to do with God’s willingness to forgive sin.
One thing I’d like to mention right away is that God’s holiness is not compromised by his forgiving sin. God is holy and though He forgives sin He remains holy. This is possible because of the basis on which God’s pardon for sin rests. God forgives us because the righteous demands of his holiness are satisfied by the death of the Lord Jesus Christ. God does not merely overlook our sin to forgive us, He applies the death of his Son to us and forgives us because the price of our sin has already been paid.
This is the way God’s love and holiness came together at the cross. Love calls for forgiveness. Holiness calls for justice. In the death of the Lord Jesus in our place, justice was satisfied so that his love had a holy basis on which to forgive us. Marvellous, how God is true to his own character yet generous toward sinful creatures all at the same time.
Now let’s look at the second part of the question. “If God really does forgive sin, how can I be certain He’s forgiven me?” Let’s look at a story from the Bible in which Jesus forgave . In Matthew 9, beginning at verse one we read how Jesus came to His own city of Capernaum and some people brought to Him a paralytic lying on a bed. When Jesus saw their faith, He said to the paralytic, "Son, be of good cheer; your sins are forgiven you." And at once some of the scribes said within themselves, "This Man blasphemes!" But Jesus, knowing their thoughts, said, "Why do you think evil in your hearts? "For which is easier, to say, `Your sins are forgiven you,' or to say, `Arise and walk'? "But that you may know that the Son of Man has power on earth to forgive sins" - then He said to the paralytic, "Arise, take up your bed, and go to your house." And he arose and departed to his house. Now when the multitudes saw it, they marveled and glorified God, who had given such power to men.
In this story, we see a case where a man was forgiven his sins by the Lord Jesus. Others, of course, questioned this. They said that only God had the power to forgive sin. So Jesus in one move demonstrated his divinity and confirmed the forgiving of the man’s sins. He asked them which was easier to forgive sins or to make this paralysed man walk and then proceeded to heal his physical body. Naturally the crowds were impressed and worshipped God because Jesus, a man, had exhibited such divine power.
I’ve often thought of how the man who was healed must have been frequently reminded of his forgiveness because it was associated with his physical healing. Every step presented the opportunity to remember that he had been forgiven. It must have made a huge impact on the way he lived his life. Whenever he was tempted to sin again, the very fact that he was mobile enough to respond to the temptation could remind him that his sins had been forgiven. The other thing, was that when any moment of doubt about his forgiveness arose, his strong healthy body would remind him of Jesus power and reassure him that God had indeed forgiven him for he had demonstrated it to the crowd by healing him as well.
What about us today. Can we be sure that we are forgiven our sins. The short answer is yes. The certainty with which I say that, comes from the fact that the Bible makes some strong declarations about the pardoned status of repentant sinners. There are several passages to which I could point, in Romans chapter 4 Paul wrote about the one who does not depend on his own efforts, but believes on Him who justifies the ungodly, his faith is accounted for righteousness, just as David also describes the blessedness of the man to whom God imputes righteousness apart from works: "Blessed are those whose lawless deeds are forgiven, And whose sins are covered; Blessed is the man to whom the LORD shall not impute sin." (vv 5-8)
In his letter to the Christians in the city of Colosse, Paul wrote this strongly-worded statement about those who are forgiven: And you, being dead in your trespasses and the uncircumcision of your flesh, He has made alive together with Him, having forgiven you all trespasses, having wiped out the handwriting of requirements that was against us, which was contrary to us. And He has taken it out of the way, having nailed it to the cross. Having disarmed principalities and powers, He made a public spectacle of them, triumphing over them in it. (Col 2:13-15)
Let me mention just one more, for the sake of time. Listen to these words from Romans chapter 8: There is therefore now no condemnation to those who are in Christ Jesus, who do not walk according to the flesh, but according to the Spirit. For the law of the Spirit of life in Christ Jesus has made me free from the law of sin and death. For what the law could not do in that it was weak through the flesh, God did by sending His own Son in the likeness of sinful flesh, on account of sin: He condemned sin in the flesh, that the righteous requirement of the law might be fulfilled in us who do not walk according to the flesh but according to the Spirit.
Those are all very strong statements about those who are forgiven their sin on the basis of the sacrificial death of the Lord Jesus Christ on the cross. They are blessed. They are made alive. They are free from any and all condemnation because Jesus who was perfect and holy in every way bore our sins in His own body on the tree, that we, having died to sins, might live for righteousness - by whose stripes you were healed. (2 Peter 2:24)
For some, the fact that the Bible declares the repentant sinner forgiven is enough. You might have wanted to go deeper - to know on what basis the Bible dares make these declarations of forgiveness. Now you do know. It is because in his death on the cross, Jesus the Christ satisfied the justice of God. God declared the Righteous One sin and punished Him accordingly so that sinners might be declared righteous and blessed accordingly. Don’t you love God for how He has worked all of this out for our blessing and His glory?