Here are two competing grains in these two verses: tares and wheat. One is evil, the other is good. The instructions given to the gatherers is to gather the tares first, bind them in bundles and burn them; but the wheat gather them into His barn. But they had to wait until the proper time—the harvest. Why? So, the reapers could tell them apart. Notice, the tares are to be taken first.
This was God’s warning to the Israelites through his general Joshua that if they let the Canaanites remain in the land of Palestine, they would no longer be driven out from before them. They would be snares, traps, scourges and thorns to the Israelites. The enemy would provide the harm that would result from Israel’s disobedience to keep them living in the land that they were promised.