Christ taught that forgiveness is a duty. No limit can be set to the extent of forgiveness (Lu 17:4) and it must be granted without reserve. Jesus will not admit that there is any wrong so gross nor so often repeated that it is beyond forgiveness. To Him an unforgiving spirit is one of the most heinous of sins (Bruce, Parabolic Teaching, 376 ff).
Ephesians 4:32 Updated American Standard Version (UASV) 32 Be kind to one another, tender-hearted, forgiving each other, just as God in Christ also has forgiven you.