The continued presence of foreign nations in the land was not an accident of history, but a deliberate spiritual test for the Israelites. This challenging environment was designed to see exactly how the people would conduct themselves among the remaining nations [מצודת דוד, מלבי״ם]. The core of this trial was whether they would obey God's commandments, which required two distinct types of response. On one hand, they had to exercise restraint, strictly avoiding intermarriage and the worship of foreign gods [מצודת דוד, מלבי״ם]. On the other hand, they carried an active duty to drive out the Canaanites, defeat them, and completely eliminate their places of worship [ביאור שטיינזלץ].
The concept of testing the people to see how they would act raises a logical question, as God already knows the future. However, the purpose of this trial was not to provide God with new information, but to benefit the Israelites themselves. God placed them in this situation so they would realize they were being tested and be inspired to repent. This approach ensured that the people could never claim they were abandoned to random chance without a fair opportunity to correct their behavior [חומת אנך].
To help the people awaken and succeed in this trial, they were reminded of three different layers of commitment to the commandments [חומת אנך]. The first layer is the fundamental obligation to obey the Creator of the world. The second layer emphasizes the moral duty and basic respect involved in continuing the traditions of their ancestors. Finally, the third layer represents absolute faith in the truth of the prophecy and teachings delivered by Moses.