Forgiveness is a gift from God. It is a portion of His grace. What you have been freely given, you should freely give away. Jesus said in Matthew 6:15 that if we do not forgive others, neither will God forgive us.
When the first missionaries arrived in Alberta, they were savagely opposed by a young chief of the Cree Indians named Maskepetoon, but he responded to the Gospel and accepted Christ. Shortly afterward, a member of the Blackfoot tribe killed his father. Maskepetoon rode into the village where the murderer lived and demanded that he be brought before him. Confronting the guilty man, he said,” You have killed my father, so now you must be my father. You shall ride with my best horse and wear my best clothes.” In utter amazement and remorse his enemy exclaimed, “My son, now you have killed me” He meant, of course, that the hate in his own heart had been completely erased by the kindness and forgiveness of the young Indian chief.