In Numbers, chapter thirty-three, verse fifty-five, if the Israelites failed to wholly drive out the wicked Canaanites and destroy their idolatrous worship centers, God would cause those Canaanites to give them trouble, and He will judge them. If the children of Israel are to be thoughtless, careless, indifferent to it, and not make use of the proper means to get rid of them, it could create future problems long term. However, on the contrary, if the Israelites were to make covenants and intermarry among them; or becoming friendly and suffering them to dwell would potentially jeopardize their relationship with God.
Now that the Israelites were to pass over Jordan, they entered again into the temptation to follow idols. The threat for them is if they spared either idols or idolaters, their sin would certainly be their punishment. They would foster vipers in their bosoms. The remnant of the Canaanites is when they made any peace with them, would be pricks in their eyes and thorns in their sides. We must expect trouble and affliction from whatever sin we indulge; that which we are willing should tempt us will vex us.
The intention of the Canaanites is for them to be out of the land: but if the Israelites learned their wicked ways, they also would be put out. Let us hear this and fear. If we do not drive out sin, sin will drive us out. If we are not the death of our lusts, our lusts will be the death of our souls.
Likewise, if the church of Jesus Christ tolerates sin in its midst, trouble, destruction, and death will come to the church and its members. God may allow His people to get hurt by the evil world that they have failed to resist. The challenge is to oppose the temptation. If we allow sin to linger, we will find ourselves thinking to consider it.