Do not make an alliance with them or show them any mercy. Deut. 7:2b TEV
Lawn care is an endless job. The alternative to a healthy, well tended lawn, is a weed patch. Failure to fertilize allows your grass to become weak and vulnerable. Weeds can then get a head start and choke out your grass.
Imagine trying to start a new lawn in a weed patch. The Israelites were entering a pagan land -- a weed patch of idolatry. God knew their faith would be challenged and gave them clear instructions for how to avoid the infiltration of idolatry into their lives. "Do not intermarry with the pagans." "Do not allow your children to intermarry with the pagans" vs. 3.
Sinning is as easy as letting our lawn go to crab grass and dandelions. Indeed, we do not need to plant weeds in our lawns. The seed is already there waiting to take over. By the same token, we already have sinful natures waiting to take over. To obey God takes work. It takes a prayerful walk with Him in the study of His Word. That is the fertilizer that keeps us spiritually strong.
Give us strength, Lord, to resist temptation and walk in your Word. Amen.