“If you say in your heart, ‘These nations are greater than I. How can I dispossess them?’
17 If thou shalt say in thine heart. Since it was a matter of great difficulty to destroy such a multitude of men, and despair itself would drive them to madness, so that it would be frivolous for the Israelites to cut off all hope of mercy, God anticipates their fear, and exhorts them to the strenuous execution of His sentence.
Here, I. The caution against idolatry is repeated, and against communion with idolaters: "Thou shalt consume the people, and not serve their gods." Deu 7:16. We are in danger of having fellowship with the works of darkness if we take pleasure in fellowship with those that do those works. Here is also a repetition of the charge to destroy the images, Deu 7:25, Deu 7:26.
Commenting on Deuteronomy 7:12-26
If thou shall say in thine heart,.... Should have secret thoughts arise in the heart, misgivings of heart, fears and doubts there, which, though not outwardly expressed, might be inwardly retained: these nations are more than I; seven to one, and perhaps anyone of them as powerful as Israel: how can I dispossess them? of the land they inherit, and take possession of it.