Why would God's people be forbidden to associate with certain nations for generations?
This isn't about arbitrary discrimination. The exclusion of Ammonites and Moabites stems from their specific actions against Israel.
Refusal of Basic Hospitality:
When Israel left Egypt, they were a vulnerable people. They passed by Edom and Moab, asking only for passage and the payment for food and water. While Edom (though related) refused passage, Moab and Ammon went further – they actively refused hospitality and, shockingly, hired Balaam to curse Israel. This wasn't just a minor slight; it was an attempt to thwart God's plan and destroy His chosen people.
A Deep-Seated Malice:
Calvin points out that their actions revealed a deliberate, malicious opposition to God's grace and the welfare of His church. They didn't just oppose Israel; they opposed God Himself by seeking to curse His covenant people. This deep impiety and hostility are the reasons for their severe and lasting exclusion from the 'assembly of the LORD.'