Forgiveness is something Christians are expected to do. Jesus described it as an obligation, like something required of a slave or servant (Luke 17:9-10). One of the reasons Christians are expected to forgive others for the sins they commit against them is because they have received forgiveness from God. Jesus said, “For if ye forgive men their trespasses, your heavenly Father will also forgive you: but if ye forgive not men their trespasses, neither will your Father forgive your trespasses” (Matthew 6:14-15). It could be that God expects his children to forgive others because it is a basic principle of his kingdom, something that everything else depends on. Without forgiveness, salvation would be worthless.
Jesus told his disciples, “Temptations to sin are sure to come, but woe to the one through whom they come!” (Luke 17:1, ESV). Jesus made it clear that sin was a part of life, but he also wanted his disciples to know there was a penalty for leading others astray. He said, “It would be better for him if a millstone were hung around his neck and he were cast into the sea than that he should cause one of these little ones to sin” (Luke 17:2, ESV). In order to avoid the temptation of sin, Jesus told his disciples, “Pay attention to yourselves! If your brother sins, rebuke him, and if he repents, forgive him, and if he sins against you seven times in the day, and turns to you seven times, saying, ‘I repent,’ you must forgive him” (Luke 17:3, ESV).
In a way, you could say that forgiveness is a type of cure for sin. It’s like putting a bandage on an open wound. If there is no forgiveness, then the wound can get infected and might lead to death. The example Jesus gave of the brother that sinned repeatedly, but repented every time, may have been meant to convey the idea that sin is like an addictive behavior. It can take a while for it to be brought under control. As long as someone is aware that what he is doing is wrong, and wants to stop doing it, the bandage of forgiveness needs to continually be reapplied. The idea being that although it may take longer, the wound will eventually be healed.
Jesus’ disciples looked at forgiveness as an act of faith. In response to Jesus’ command to forgive him every time a brother repents, it says in Luke 17:5, “And the apostles said unto the Lord, increase our faith.” Rather than faith, Jesus implied forgiveness required a forced act of obedience. The only thing that would convince someone to do it would be harsh discipline. Jesus reminded his disciples that they were called to serve God and commanded to forgive others. He then concluded, “So you also, when you have done all that you were commanded, say, ‘We are unworthy servants; we have only done what was our duty” (Luke 17:10, ESV).