Deuteronomy 20:15-18

15Thus you shall do to all the cities that are very far from you, which are not cities of the nations here. 16But ain the cities of these peoples that the Lord your God is giving you for an inheritance, you shall save alive nothing that breathes, 17but byou shall devote them to complete destruction,
That is, set apart ( devote) as an offering to the Lord (for destruction)
the Hittites and the Amorites, the Canaanites and the Perizzites, the Hivites and the Jebusites, as the Lord your God has commanded,
18that dthey may not teach you to do according to all their abominable practices that they have done for their gods, and so you esin against the Lord your God.

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