Deuteronomy 7:16

16.And thou shalt consume all the people. It is plain from the second part of the verse wherefore He commands the people of Canaan to be destroyed, when He forbids their gods to be worshipped. This precept, therefore, corresponds with the others, where He dooms in like manner these nations to utter destruction. I now pass over what I have explained elsewhere, i.e., that the vengeance which God exercised against these obstinate and ten-times lost people cannot be ascribed to cruelty. For since 400 years ago it had been said to Abraham that their iniquity was not yet full, they could not be treated with severity equal to their deserts, when they had so licentiously and wickedly abused God’s long-suffering. But we must take notice of God’s design in so particularly enjoining on the Israelites utterly to destroy whatever should be found there; for besides that He had once doomed them all to the destruction they merited, He would have the land also, in which His name was to be invoked, purged from all pollutions. Now, if any of the old inhabitants had survived, they would soon have endeavored to revive their corruptions, and since the Israelites were otherwise more disposed than enough to superstition, they would easily have been attracted to the worship of idols. This, then, is the reason why God forbids them to shew these people any humanity or clemency, as I have reminded you to be clear from the context; for these things stand in connection, that they should not spare the nations nor worship their gods. The reason which is subjoined, “for it will be a snare or stumblingblock to you,” must be extended to the whole context, viz., that it would be fatal to the Jews if they should spare the nations which would allure them to impiety.