How can God be merciful and just at the same time?

Two of God’s attributes that seem to contradict one another are His mercy and His justice.  How can a God who is merciful judge people for their sin?  How can a God who is committed to justice have mercy on those who do evil?  These two apsects of God's nature seem to cancel one another out, and therefore God can't be both...can He?

Yet throughout Scripture, God is depicted as both.  And this should really not be too surprising, for if God is perfect (Matt. 5:48), then He must be perfectly merciful and perfectly just.  A beautiful illustration of this can be found in the words of the LORD to the prophet Hosea:

"And I will make for them a covenant on that day
with the beasts of the field,
the birds of the heavens,
and the creeping things of the ground.

And I will abolish the bow,
the sword,
and war from the land,
and I will make you lie down in safety. 

And I will betroth you to me forever.
I will betroth you to me in righteousness and in justice,
in steadfast love and in mercy. 
I will betroth you to me in faithfulness.
And you shall know the LORD."   

(Hosea 2:18-20; ESV)

Here we see God speaking of His future relationship to His people.  In this passage, God’s justice is linked to His righteousness and His mercy is linked to His love.  Indeed these attributes flow from His very nature.  God is a just God because He is righteous—righteousness entails justice.  And God is a merciful God because He is the embodiment of love—and love entails mercy.  Rather than being in conflict, these two qualities are two sides of the same coin. 

Another example of both God’s justice and mercy is found in the book of Jonah.  Because Nineveh--the capital of the dreaded Assyrian Empire--was so wicked, they were deserving of God’s just judgment: utter destruction.  This is a judgment that would've elicited cheers and shouts of joy throughout the Ancient Near East among the peoples whom Assyria had oppressed, enslaved or destroyed!  However, God actually sent the Hebrew prophet Jonah to warn them of this impending judgment!  Then, as if that wasn't enough, when the city as a whole repented and sought the mercy God, He relented and did not destroy them--thus making Jonah appear to be a false prophet!  In one of the Bible's best temper-tantrums, Jonah makes the following comment:

"O LORD,
is not this what I said when I was still in my country?
That is why I made haste to flee to Tarshish!
For I knew that you are a gracious God and merciful,
slow to anger and abounding in grace, and relenting from disaster." 
(Jonah 4:2; my translation)

Jonah was upset because he wanted the Ninevites to be destroyed as a just punishment for all their evils.  Contrary to the way this story is often told, Jonah initially fled from God's calling not because he was scared to go to Ninevah, but because he knew that God was merciful and would not destroy the city if they repented.  Jonah didn't want them to have the chance to repent; he wanted to them to die!  And so when he finally did preach God's warning to Ninevah's citizens and they actually did repent, he felt that God’s justice had not been served. 

Like many of us, Jonah could not see the relationship between God’s mercy and His justice...however, the two go hand-in-hand.  And notice that these two examples come from the Hebrew Bible, aka. the "Old Testament", in which many people think God is nothing but a grumpy, vindictive cosmic executioner looking to "smite" people for the sheer joy of it!  (This shows the degree to which most people are ignorant of the actual content of the Hebrew Scriptures.)

This combination of mercy and justice has no greater example however than that of the cross of Christ.  For it was there that they were both most fully revealed. 

God, in His justice, could not overlook the sin of humanity.  A human judge who lets a guilty party go with no punishment is not a just judge; how much more then does this apply to God!  No, there had to be atonement for human sin by humanity. 

However, in His mercy, God Himself made that atonement by receiving the full punishment of His justice in the person of Jesus:

“...that is, in Christ God was reconciling the world to himself,
not counting their trespasses against them,
and entrusting to us the message of reconciliation” 
(2 Corinthians 5:19; ESV).

It was here at the cross that God’s justice and God’s mercy met head-on.  And that is the very core of the Gospel message.  (Incidentally, this is one of the biggest problems with any view that denies the full divinity of Christ--if God was not somehow, in some way fully present in the person of Jesus, his death on the cross could not atone for any sin but his own and the entire Gospel message would be meaningless.)

The balance seen in Scripture between mercy and justice should serve as a model for the Church today in how it manifests justice and mercy in its ministry to the world.  The Church should passionately seek to show mercy to those who do not deserve it (really, do any of us deserve it??), while at the same time maintaining the righteous standards of God’s justice in dealing with the reality of sin in the world--particularly among those claiming to be God's people. 

Paul’s charge to the Church at Philippi was to “be blameless and innocent, children of God without blemish in the midst of a crooked and twisted generation, among whom you shine as lights in the world” (Philippians 2:15; ESV).  Only by doing this can  the Church faithfully mirror both God’s mercy and God's justice to the world around us.