In the thirteenth chapter, Keller perhaps discusses the area of Christianity where the experiencing of the intimacy and awe of God comes into play and does so with a whole whack of tension. This area is the area of forgiveness of sins. The experiencing of intimacy is profoundly experienced in the free forgiveness of our sins. But the experiencing of the awe of God is also experienced when we contemplate the infinite cost this free forgiveness required.
Keller desires to keep this biblically informed tension in the forefront in this chapter. He writes,
Only against the background of the Old Testament, and the great mystery of how God could fulfill his covenant with us, can we see the freeness of forgiveness and its astounding cost. It means that no sin can now bring us into condemnation, because of Christ's atoning sacrifice. It also means that sin is so serious and grievous to God that Jesus had to die. We must recognize both of these aspects of God's grace or we will lapse into one or the other of two fatal errors. Either we will think forgiveness is easy for God to give, or we will doubt the reality and thoroughness of our pardon. (207)Forgiveness is a beautiful thing. Even in earthly relationships, one would be hard pressed to find a sweeter, more intimate and affecting idea than forgiveness. And yet, when forgiveness comes from the infinite and perfectly holy Creator of the universe, and the cost of his infinite and perfectly holy Son, the glory of forgiveness starts to be seen in its massively majestic splendour. Keller continues,
All those who are in Christ must and will be forgiven Why? He has taken the punishment and paid the debt for all their sins. It would be unjust of God--and unfaithful to his covenant with us to receive two payments on the same debt, so it would be unjust for him not to forgive us. This profound assurance and security transforms repentance from being a means of atoning for sin into a means of honoring God and realigning our lives with him. (209)The debt-paying sacrifice of our glorious Saviour assures our forgiveness which also assures the almost unbelievable reality of an intimate relationship with God! And the awe-inducing reality of what this actually cost, and what Christ actually did to secure this blessing, should leave us in a state of reverence beyond normal experience. Such is the nature of grace; forgiveness that is free and infinitely costly.