During the summer between my first and second years at the Episcopal Theological School (now the Episcopal Divinity School), I was a student chaplain at a state mental hospital. One day I was passing through a ward on my way to the ward to which I was assigned. I was walking quickly, chiefly because I was late, but also because I was aware that I was intruding on the living space of the ward's patients. Before I could make my way to the exit, a man approached and asked if God could forgive him. Not wanting to spend too much time in conversation, I asked him if he ever murdered anyone. He looked shocked and told me that, of course, he never. I replied that it was certain that God could forgive him, because God had forgiven Paul, who, at the very least, had conspired in the murders of the first Christain martyrs.
Paul understood the nature of sin and that it is in our human weakness that we fall under the power of sin. Paul knew that humans could not, by their own strength, escape from the power of sin. Having discovered for himself how God deals with sin and with sinners, Paul preached the Good News of forgiveness and reconciliation to Jew and Gentile alike.
Roman Catholic priest and theologian James Alison has suggested that the experience of the Resurrection for the disciples on the first Easter was the experience of being forgiven. All of them had, in one way or another, been unfaithful to Jesus - Peter in a very public way, but all of the rest in less public ways. When Jesus appeared to them, he didn't dress them down or chew them out for having failed him - something which most of us would do - but he simply said, "Peace be with you." Peace - the gift of being forgiven, the gift of being reconciled with Jesus, reconciled with God.
Alison has also suggested that God understands sin as that which can be forgiven. Far too many Christians think that God's attitude to sin is best reflected in the bumper sticker, "Jesus is coming back and he's pissed." But that certainly isn't the way that Jesus came either in his ministry or in his Resurrection. Jesus came with forgiveness and the power to transform us , and why should we expect that in his coming again it would be any different?