Deuteronomy 12:2

Ye shall utterly destroy all the places wherein the nations which ye shall possess, whose land they would make their own by conquest, served their gods, upon the high mountains and upon the hills, for the idea was that the worshipers were nearer to the Deity at these places, and under every green tree, for the heathen loved groves, whose mysterious shadows furnished them the religious thrill which they felt to be essential;