The Institutes, Book 7
Renouncing Badly and Not Renouncing at All
To those, then, who say they have renounced this world, and afterwards, overcome by lack of faith, are afraid of losing their worldly goods, a command is given in a hidden sense in Deuteronomy: “If any man is afraid and fainthearted, let him not go out to war. Let him go back and return home, so that he does not make the hearts of his brothers afraid, as he himself is timid and frightened.” What could one want plainer than this testimony? Does not Scripture clearly prefer that they should not take on themselves even the first stages of this profession and its name, rather than turn others back from the perfection of the gospel by their persuasion and bad example, and weaken them by their faithless terror? So they are told to withdraw from the battle and return to their homes, because a man cannot fight the Lord’s battle with a double heart. For “a double-minded man is unstable in all his ways.”
As in the parable in the Gospel, they should reckon that he who goes out with ten thousand men against a king who comes with twenty thousand cannot possibly fight, and so they should ask for peace while the other is still a long way off. That is, it is better for them not even to take the first step toward renunciation than afterwards to follow it up coldly and involve themselves in still greater dangers. For “it is better not to vow than to vow and not pay.” And it is well put that the one comes with ten thousand and the other with twenty. For the number of sins that attack us is far larger than the number of virtues that fight for us. But “no one can serve God and mammon.” And “no one who puts his hand to the plow and looks back is fit for the kingdom of God.”