[E]ven more pronounced than Christ’s teaching on God’s mercy towards man is his instruction on man’s mercy towards man. The Lord is most clear and most insistent upon his injunction that his followers are to forgive their fellow men.
There is no limit to the forgiveness we must offer each other. We are to forgive the transgressor “not seven times, but seventy-seven times” (Mt. 18:21-22). Do not condemn, do not judge, but “be merciful, just as also your Father is merciful” (Lk. 6:36-37). In the Sermon on the Mount, the Lord teaches that even mere anger or ill will towards another is a sin that demands repair. We cannot approach God with enmity of any sort against a neighbor (Mt. 5:21-26). The one human action (as opposed to praise and petition) referenced in the Lord’s Prayer is the act of forgiveness.
The Christian God is merciful to the repentant, and the Christian is forgiving. This is perhaps his most fundamental outward attribute. ~Christian Browne, Recalling the Central Gospel Message