Deuteronomy 20:18

18 that they not teach you to do after all their abominations, which they do unto their gods, lest ye should sin against the LORD your God.

Deuteronomy 20:18 Meaning and Commentary

Deuteronomy 20:18

That they teach you not to do after all their abominations,
&c.] This is another reason why they were to be utterly destroyed, not only because of the abominations which they committed, but to prevent the Israelites being taught by them to do the same; wherefore, as before observed from Jarchi, such as became proselytes were suffered to live among them, because there was no danger of idolatry from them, which even proselytes of the gate renounced; and though all other abominations are included, yet this is particularly respected, as appears from the following clause:

which they have done unto their gods;
to the honour of whom not only many superstitious rites and ceremonies were performed, and idolatrous actions committed, but acts of lewdness, and even unnatural uncleanness:

so should ye sin against the Lord your God;
a sin the most provoking to him, as the sin of idolatry was; and cause his anger to rise to such a degree, as to suffer them to be carried captive from the land he gave them to inherit; and which afterwards, was the case, and that through learning the manners and customs of these people; see ( Psalms 106:34-42 ) .

Deuteronomy 20:18 In-Context

16 Only of the cities of these peoples, which the LORD thy God gives thee for an inheritance, thou shalt save alive nothing that breathes;
17 but thou shalt utterly destroy them: the Hittite and the Amorite, the Canaanite and the Perizzite, the Hivite and the Jebusite, as the LORD thy God has commanded thee,
18 that they not teach you to do after all their abominations, which they do unto their gods, lest ye should sin against the LORD your God.
19 When thou shalt besiege a city a long time, in making war against it to take it, thou shalt not destroy the trees thereof by forcing an axe against them, for thou may eat of them; and thou shalt not cut them down (for the tree of the field is man’s life) to employ them in the siege.
20 Only the trees which thou knowest that they are not trees for food, thou shalt destroy and cut them down; and thou shalt build bulwarks against the city that makes war with thee, until it is subdued.
The Jubilee Bible (from the Scriptures of the Reformation), edited by Russell M. Stendal, Copyright © 2000, 2001, 2010