The Problem of Mercy & Justice

I speak often about the problem of evil. But another big problem in the Bible, especially the Old Testament, is the problem of mercy and justice. Take the following verse:

Exodus 34:5-7

New Revised Standard Version (NRSV)

⁵ The Lord descended in the cloud and stood with him there, and proclaimed the name, “TheLord.”^[a] 6 The Lord passed before him, and proclaimed,

“The Lord, the Lord,
a God merciful and gracious,
slow to anger,
and abounding in steadfast love and faithfulness,
⁷ keeping steadfast love for the thousandth generation,
forgiving iniquity and transgression and sin,
yet by no means clearing the guilty,
but visiting the iniquity of the parents
upon the children
and the children’s children,
to the third and the fourth generation.I speak often about the problem of evil. But another big problem in the Bible, especially the Old Testament, is the problem of mercy and justice. Take the 

Here God is said to be so merciful it is hard to offend Him. Yet is punishment is so extreme that it is visited even on the descendants of sinners. And all through the prophets, God is seen as transcendentally merciful, as merciful beyond measure, as merciful in a way that makes human mercy look insignificant by comparison. Yet these same prophets proclaim that God forgets not one sin, and that all sin is punished as it deserves to be. God is seen as 'perfectly merciful' and 'perfectly just'. Yet justice is to give people what they deserve, and mercy to refrain from giving people what they deserve. Mercy and justice sit in tension with one another. How can God be 'perfectly merciful' and 'perfectly just'? It seems contradictory.

So alongside the problem of evil, you have the problem of mercy and justice, both of which are present in the Old Testament. I think facing these problems helps us understand the need for Jesus. For it is my belief that Jesus came in part to help us understand the presence of innocent suffering in the world, and to help us understand how mercy and justice are reconciled in God.