What did Jesus say about forgiveness?
Jesus said a great deal about forgiveness and how important it is for us to forgive each other. Jesus encouraged us to think about it in God's terms. God forgives us so we should also forgive each other.
More complicated answer
Forgiveness is actually a very complicated subject. If we forgive people then does this mean that they are let off any responsibility concerning the wrongs they have committed? If God forgives us does this mean that God forgives us all or does God only forgive people who do certain things?
Let's think about God's forgiveness first. God showed that he takes wrongdoing and its effects very seriously, so seriously in fact that Jesus goes to the cross because of the consequences of all the wrong that is done. When we talk about God being forgiving we must not forget that God is also just and this means that in every situation there must be a penalty for anything that is done wrong.
God takes on himself the consequences for any wrong that we do to God so that forgiveness also brings with it God's was of dealing with those consequences.
Jesus taught that this forgiveness is offered to everyone but not everyone will accept it.
For if you forgive men when they sin against you, your heavenly Father will also forgive you. But if you do not forgive men their sins, your Father will not forgive your sins. - Jesus in Matthew 6:14-15
Jesus told a parable about forgiveness known as 'the unmerciful servant' Matthew 18:21-35 to make the point that we should learn to forgive without limits.
People often find it hard to forgive because they feel that somehow to forgive is to let someone off the guilt of their crime. Jesus never said that there would be no justice for those who are forgiven but instead chooses to pay the penalty for the crimes of others.
“The personal desolation Christ is experiencing on the cross is what you and I should be experiencing--but instead, Jesus is bearing it, and bearing it all alone.Why alone?He's alone so that we might never be alone.” ― C.J. Mahaney, Living the Cross Centered Life: Keeping the Gospel the Main Thing