"And the Lord changed his mind about the disaster that he planned to bring on his people."
Here the King James translation is more accurate: "And the Lord repented of the evil which he thought to do unto his people." Grace, it seems, is not God's first inclination of how to respond to the evil in the world. Thankfully, God's first response is not his final response.
In reading through Genesis, we quickly learn of God's first response. Banning Adam and Eve from the garden and sentencing them to hard labor (two meanings to that phrase). And then there was this flood. And then confounding the speech so that humanity might never again act as one.
And yet even within this rapid sequence detailing the sinfulness of humanity and God's judgment there is repentance. Except it is not humanity that repents, but God. A rainbow declares from the heavens that never again will God give into his desire to destroy all evil. It didn't work. God recognized that. God repented. "The best laid plans of mice and men (and God) go awry."
It's not that God was and is not justified in his initial response to our sinfulness. For the Israelites to fashion a golden calf on the flanks of Mt Sinai, even as Moses was receiving the Ten Commandments directly from God's hand-- well that was not going to go over well with the Lord. His initial response, "Let me have at them, Moses." And it is Moses who intercedes on behalf of the people, calling forth from God a gracious remembrance of the promises that God has made. And God repents. (Moses, too, would have his moment when he actually witnessed the depravity of the people, but that's another story.)
And then, in the wake of his repentance, is God's decision to be "a gracious God and merciful, slow to anger, and abounding in steadfast love, and ready to relent from punishing." (Jonah 4:2)
God's inclination to grace towards us, is rooted in his own experience of repentance. Many times God's wrath would be kindled against his rebellious and wayward people, and many time he would repent, and then, in the end, would respond by loving us even while we were yet sinful. Is God's willingness to accept and forgive us a direct result of his own experience of desiring to rain down fire from heaven, and yet, letting go of the anger, and responding with love instead? This is the witness of the scriptures.
For this reason, God doesn't give up on the likes of Paul. Paul's initial response to the followers of Jesus was to seek to destroy these blasphemers. Not altogether unlike God's response to the golden calf. "Been there, done that."
Enter Jesus. Welcoming sinners and eating with them. Grace abounds. Gone is the righteous anger and indignation. In its place is a love that is steadfast and transforming. There is Paul, in one moment, supervising the stoning of Stephen and in the next, carrying the message of the Gospel to the world -- not to mention writing the bulk of the New Testament which of course defines the Christian faith for all time.
Jesus came to save sinners. God repented of the evil he intended. And the result is Paul. And the result is you and me, sinful though we be, gathered together as the body of Christ. Thank God for repentance, especially, his own.