"Do not be deceived: God cannot be mocked. A man reaps what he sows. Whoever sows to please their flesh, from the flesh will reap destruction; whoever sows to please the Spirit, from the Spirit will reap eternal life."--Galatians 6:7-8
It's a concept that is widely accepted as truth, even by those who don't believe in Christ or in the Bible. Some people, in an attempt to separate the concept from its Scriptural roots, refer to it as "karma." Even as the secular world tries to deny its origin, however, there is no denying the concept: What goes around, comes around.
For those of us who are Christians, it goes even deeper. We not only acknowledge the concept, but we acknowledge the source. Moreover, we know that because God is in control, the law of sowing and reaping is absolute. Whatever we sow, whether it be spiritual or sinful, whether it be right or wrong, will certainly produce its harvest in our lives.
What does this have to do with Christian spec-fic? I see the genre being fueled by the concept of good vs. evil, of the spirit vs. the flesh, of God vs. the devil. Christian spec-fic is a great tool for illustrating the concept for the modern world--stories whose main thrust revolves around characters reaping what they have sown.