In Matthew 13, we encounter the parable of the wheat and the tares, along with its interpretation.
According to the parable, God plants in his field some good seed, which grows up to be wheat. The good seed represents the children of the kingdom. But an enemy, the devil, inserts bad seed into the field, and it matures into tares. The bad seed symbolizes the children of the devil. God's servants want to uproot the tares, but God stops them, warning that such a drastic endeavor could hurt the good as well as the bad. And so God allows them to grow together until the harvest, when he will gather up the wicked into the fire.
I have two problems:
First of all, this parable doesn't exactly mesh with my understanding of the Christian narrative. In the story that I've always heard, the entire human race is sinful, but God has managed to save a few, either through their own free will or God's unalterable decree. It's not so much a matter of having all these children of the kingdom, only for Satan to insert some of his bad seed into the mix. On the contrary, we have all of these children of the devil in the world, only for God to insert some of his good seed into the equation. Or more than that: God transforms a small portion of the bad seed into good seed. And so God is disrupting Satan's world, not vice versa.
Some try to argue that the field is the church. And, indeed, Satan does work overtime to disrupt that. According to the New Testament, Christians should watch out for unsavory types who can enter Christ's body. They may be false teachers, or oppressors, or blatant sinners, but, whoever they are, they can have an adverse affect on Christ's flock, if it is not careful. That's why there are numerous passages about how to identify a true servant of God. There were plenty coming into the church who were serving the other guy!
But I have problems seeing the field as the church, since Jesus identifies it as the world (Matthew 13:38). And we know from Scripture that, in the world, the children of the kingdom are a small minority (Matthew 7:14).
Here's a possible solution: Perhaps Satan was trying to hinder God's plan in advance. E.W. Bullinger has an interesting view on the Canaanites. According to him, God was planning to give Abraham the Promised Land, and Satan didn't want that. Consequently, Satan inserted all these big, bad, vicious Canaanites into the land, making it more difficult for the Israelites to possess it. Similarly, God desired to establish his kingdom in the world, and Satan sought to thwart it by planting all of his bad people into it, people who could hinder God's redemptive purposes before God actually acted to get them off the ground. This scenario may work. But I have problems viewing anyone as an irrevocable child of Satan.
My second issue is this: Why's God want to wait before he uproots the wicked? He says he's afraid he'll hurt the righteous as well, but won't that be a problem whenever he decides to intervene? I mean, when you go after a large entity like (say) the world, you're going to take down all kinds of people, good and bad. What is it about the harvest that makes it easier for God to separate the good from the evil?
Some may say that, at the harvest, God will be able to distinguish clearly the wheat from the tares, since they'll be fully grown. But doesn't God already know who is good and who is bad? Why's he need to wait and see?
Is this parable a prooftext for the pre-tribulation rapture, the belief that God will take the righteous into heaven and leave the wicked on earth to be destroyed? I don't know. Even Tim Lahaye (a prominent pre-tribber) presents conversions after the rapture (the "tribulation saints"), plus his God pleads with sinners to repent throughout the tribulation. So, even in the pre-trib scenario, there remains the problem of God destroying the righteous with the wicked.
Does God want to give all people time to take sides before he harvests? Maybe. But the parable doesn't really present any of the bad seed choosing to become good seed. Rather, there is good seed, and there is bad seed, period.
The wheat and the tares are really intertwined at the beginning, which is why God is reluctant to uproot the tares. Perhaps God wants to give the wheat a chance to disentangle itself from the world's corruption, before he steps in to judge. I'm reminded of I Peter 4:17-18: "For the time has come for judgment to begin with the household of God; if it begins with us, what will be the end for those who do not obey the gospel of God? If it is hard for the righteous to be saved, what will become of the ungodly and the sinners?" (NRSV).
This is a hard parable!