I was reading through 1 Clement recently, a letter from the leader of the church of Rome addressed to the church in Corinth. The problem with which the discussion opens is a detestable and unholy schism, so alien and strange to those chosen by God (1.1) which evidently has taken place in the latter church because of jealousy and other such vices (3.2-4). Clement then proceeds to recount past instances of righteousness and repentance which was rewarded by God with salvation, as well as instances of disobedience which were met with judgment.
After recalling these things, he writes:
Let us therefore be humble, brothers, laying aside all arrogance and conceit and foolishness and anger, and let us do what is written. For the Holy Spirit says: "Let not the wise man boast about his wisdom, nor the strong about his strength, nor the rich about his wealth; but let the one who boasts boast in the Lord, to seek him and to do justice and righteousness." Most of all, let us remember the words of the Lord Jesus, which he spoke as he taught gentleness and patience. For he said this: "Show mercy, so that you may receive mercy; forgive, so that you may be forgiven. As you do, so shall it be done to you. As you give, so shall it be given to you. As you judge, so shall you be judged. As you show kindness, so shall kindness be shown to you. With the measure you use it will be measured to you." With this commandment and these precepts let us strength ourselves, so that we may humbly walk in obedience to his holy words (13.1-3).
It is fascinating to me that Clement recommends mercy, forgiveness, and kindness as ways of avoiding the judgment and punishment of God. Why is it exactly that things which are effectively alternatives to judgment will save one from them, whereas the failure to be merciful, to forgive, and to be kind are met with unmercy, unforgiveness, unkindness? Doesn't God somehow work against himself, compromise his own standards, if he chooses to punish the persons who adopted a morality of punishment?
If we suppose God punishes for its own sake, exacts judgment purely for the sake of retribution, we might have a contradiction of sorts: for then he exempts those from judgment who take a moral stance which is opposed to judgment, whereas those who affirm punishment and judgment are then punished and judged for it. Either judgment and punishment are values or they are not! If they are, what is the matter with my taking judgment into my own hands? What is the matter with me refusing to forgive, if I have every right to be resentful? After all I couldn't even in principle be called to forgive if there weren't something to forgive, and if there is something to forgive, there is something to resent as well.
But we can escape the contradiction of values if we reject that God is interested in punishment and judgment for their own sake. We may instead interpret the punishment and judgment of the unmerciful and unforgiving as educative, a way in which God awakens those who refuse to forgive to the gravity of their refusal. The refusal to forgive puts the unforgiven person in hell, just as all of humanity would be in hell if God had not forgiven us. It may be, therefore, that God engages in punishment and judgment precisely to show persons who do likewise that it's not good; it's not something they would desire for themselves, and consequently they ought not to impose it upon others (cf. Mt 7.12, the golden rule).
We may even strengthen the point by appeal to a more robust, realized atonement theology. Suppose you think that human sin and the like was actually and completely atoned by Christ's act of faithfulness, independently of the beliefs anyone might have about the matter. Of course, faith and belief in the message of this salvation is certainly a condition to experiencing it and benefiting from it, just as it may be a condition of enjoying some lottery money that you believe you've won it. But it wouldn't be the faith itself which realizes the atonement for your sins; it would just be a way of subjectively appropriating an antecedent objective truth.
Now on a picture like this, it may be that God expects Christians and others to forgive one another insofar as Christ has already accomplished atonement for all of human sin (cf., e.g., Eph 4.32: Forgive one another as God in Christ has forgiven you.) If a person were to refuse to forgive, to be kind, to be merciful, this could be understood to be a refusal or denial of the completion of Christ's work, as if Christ's act did not work atonement for all human sin. Therefore such a person is consequently approached and treated by God as if Christ did not accomplish atonement for her sins either: she is judged, condemned, and punished because -- as she should accept, given her behavior -- there has been no atonement for her sins. Of course there is no undoing Christ's accomplished work. There can be no changing that in Christ God has accomplished atonement for the whole world (1 John 2.2). But God acts as if there were no atonement when we act as if there were no atonement, so that we can be brought to treat others as we would like to be treated as well, and to be reminded of the truth of Christ's accomplished work.