The Institutes, Book 4
Why No One Is Admitted Easily
Boundless glory hereafter is promised to those who serve God faithfully and hold fast to him according to the rule of this way of life. In the same way, the severest penalties await those who have carried it out carelessly and coldly, and have failed to show him fruits of holiness that match what they professed or what people believed them to be. For, as Scripture says, “It is better that a man should not vow than that he should vow and not pay”; and, “Cursed is he who does the work of the Lord carelessly.”
That is why we turned you away for a long while. It was not that we did not desire with all our hearts to secure your salvation and the salvation of all, nor that we did not care to go out even a long way to meet those who long to be converted to Christ. It was for fear that, if we received you rashly, we might make ourselves guilty of thoughtlessness in the sight of God, and bring a heavier punishment still on you, if you had been admitted too easily, without realizing the responsibility of this profession, and had afterward turned out a deserter or lukewarm. So you ought first to learn the real reason for renouncing the world. When you have seen it, you can be taught more plainly, from that reason, what you ought to do.