wrath and love

Let us not trifle with God or trivialize his love. We will never stand in awe of being loved by God until we reckon with the seriousness of our sin and the justice of his wrath against us. But when, by grace, we waken to our unworthiness, then we may look at the suffering and death of Christ and say, “In this is love, not that we have loved God but that he loved us and sent his Son to be the [wrath-absorbing] propitiation for our sins” (1 John 4:10). ~ John Piper, Fifty Reasons why Christ Came to Die

From Theological Dictionary of the New Testament, "Only he who knows the greatness of wrath will be mastered by the greatness of mercy. The converse is also true: Only he who has experienced the greatness of mercy can measure how great wrath must be. For the wrath of God arises from His love and mercy. Where mercy meets with the ungodly will of man rather than faith and gratitude, with goodwill and the response of love, love becomes wrath."

John Stott uses this concept in The Cross of Christ.

"We saunter up to God to claim His patronage and friendship; it does not occur to us that He might send us away. We need to hear again the apostle Peter's sobering words: 'Since you call on a Father who judges each man's work impartially, live your lives....in reverent fear' (1 Pet 1:7). In other words, if we dare to call our Judge our Father, we must beware of presuming on Him. It must even be said that our evangelical emphasis on the atonement is dangerous if we come to it too quickly. We learn to appreciate the access of God which Christ won for us only after we have first seen God's inaccessibility to sinners. We can cry 'Hallelujah' with authenticity only after we have cried 'Woe is me, for I am lost.' In Dale's words, 'it is partly because sin does not provoke our own wrath, that we do not believe that sin provokes the wrath of God'.

We must, therefore, hold fast to the biblical revelation of the living God who hates evil, is disgusted and angered by it, and refuses ever to come to terms with it. In consequence, we may be sure that, when he searched in His mercy for some way to forgive, cleanse and accept evil-doers, it was not along the road of moral compromise. It has to be a way which was expressive equally of His love and of His wrath. As Brunner put it, 'where the idea of the wrath of God is ignored, there will also be no understanding of the central conception of the Gospel: the uniqueness of the revelation of the Mediator'. Similarly, 'only he who knows the greatness of wrath will be mastered by the greatness of mercy'.

...If we bring God down to our level and raise ourselves to His, then of course we see no need for a radical salvation, let alone for a radical atonement to secure it. When, on the other hand, we have glimpsed the blinding glory of the holiness of God, and have been so convicted of our sin by the Holy Spirit that we tremble before God and acknowledge what we are, namely 'hell-deserving sinners', then and only then does the necessity of the cross appear so obvious that we are astonished we never saw it before."

There is an inevitable collision between Divine perfection and human rebellion. There's an enormous gulf between God as He is and us as we are. Neither our sin nor our guilt alone is what separates us, but also the Divine reaction towards guilty sinners. God's nature demands that He express his holy love without compromising his holiness, and his holiness in judging sinners without frustrating his love.

The idea that God is Holy is foundational to Biblical religion and sin is incompatible with his holiness. Closely related to Gods holiness is his wrath, which is his holy reaction to evil.