The Secret of Paul's Success by George Bernard Shaw

Paul must soon have found that his followers had gained peace of mind and victory over death and sin at the cost of all moral responsibility; for he did his best to reintroduce it by making good conduct the test of sincere belief, and insisting that sincere belief was necessary to salvation. But as his system was rooted in the plain fact that as what he called sin includes sex and is therefore an ineradicable part of human nature (why else should Christ have had to atone for the sin of all future generations? ) it was impossible for him to declare that sin, even in its wickedest extremity, could forfeit the sinner's salvation if he repented and believed. And to this day Pauline Christianity is, and owes its enormous vogue to being, a premium on sin. Its consequences have had to be held in check by the worldlywise majority through a violently anti-Christian system of criminal law and stern morality.

But of course the main restraint is human nature, which has good impulses as well as bad ones, and refrains from theft and murder and cruelty, even when it is taught that it can commit them all at the expense of Christ and go happily to heaven afterwards, simply because it does not always want to murder or rob or torture.