Note 28 at Eph. 4:32: The basis of our ability to forgive others is the fact that we have been forgiven ourselves. You can't give what you don't possess. If we aren't walking in the forgiveness of God, we won't minister it to others. Since we have been forgiven, we can forgive others in the same way that God for Christ's sake forgave us.

He forgave us before we repented or asked for forgiveness. The offense against Him was infinitely greater than any offense we have ever suffered. So, since He forgave us, we can forgive anyone.