וְאָכַלְתָּ֣ אֶת־כָּל־הָֽעַמִּ֗ים אֲשֶׁ֨ר יְהוָ֤ה אֱלֹהֶ֙יךָ֙ נֹתֵ֣ן לָ֔ךְ לֹא־תָחֹ֥ס עֵֽינְךָ֖ עֲלֵיהֶ֑ם וְלֹ֤א תַעֲבֹד֙ אֶת־אֱלֹ֣הֵיהֶ֔ם כִּֽי־מוֹקֵ֥שׁ ה֖וּא לָֽךְ׃ (ס)
און זאָלסט פֿאַרצערן אַלע אומות װאָס ה׳ דײַן גאָט גיט דיר; דײַן אױג זאָל זיך ניט דערבאַרימען אױף זײ; און זאָלסט ניט דינען זײערע געטער, װאָרום דאָס װעט דיר זײַן אַ שטרױכלונג.
Ibn Ezra
you will consume We are commanded to destroy them, like someone consuming bread, as evidenced by the subsequent phrase your eye shall have no pity.
Sforno
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
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.