וְאָכַלְתָּ֣ אֶת־כָּל־הָֽעַמִּ֗ים אֲשֶׁ֨ר יְהוָ֤ה אֱלֹהֶ֙יךָ֙ נֹתֵ֣ן לָ֔ךְ לֹא־תָחֹ֥ס עֵֽינְךָ֖ עֲלֵיהֶ֑ם וְלֹ֤א תַעֲבֹד֙ אֶת־אֱלֹ֣הֵיהֶ֔ם כִּֽי־מוֹקֵ֥שׁ ה֖וּא לָֽךְ׃ (ס)
네 하나님 여호와께서 네게 붙이신 모든 민족을 네 눈이 긍휼히 보지 말고 진멸하고 그 신을 섬기지 말라 그것이 네게 올무가 되리라
Sforno on Deuteronomy
לא תחוס עיניך עליהם ולא תעבוד את אלוהיהם. By not ignoring idolatry in your country by people remaining there you will ensure that no Israelites will worship such deities. If you will turn a blind eye to their practices they will undoubtedly lead you into sin.
Or HaChaim on Deuteronomy
ואכלת את כל העמים, "You shall consume all these nations, etc." This is a positive commandment. Moses continues that this commandment applies to the nations whom G'd delivers into our hands (the seven Canaanite tribes). There is a clear implication that if the Israelites were to be tardy in carrying out this commandment this would be tantamount to despising a divine gift.
Rabbeinu Bahya
ואכלת את כל העמים, “you will consume all the nations.” When you will utterly destroy them the result will be as if you had eaten them as one eats bread. This is in line with what Calev had said when he came back from the spying mission 38 years earlier when he told his compatriots that the Canaanites “are our bread” (Numbers 14,9).