Not only are the idol worshipers sacrificing in the valleys, but they worship on the mountains as well! Throughout the whole country they are following Canaanite religious customs.

Upon a high and lofty mountain you have set your bed: A high and lofty mountain may refer to Jerusalem or to high places in general since they were considered ideal worship sites (see the comments on 15.2). You have set your bed is a euphemism for having sex. Good News Translation is quite explicit. As in verse 5, the idol worshipers are having sex with cult prostitutes in order to increase their own fertility and the fertility of their crops and animals. The noun bed picks up the keyword from verse 2, but here it refers to sex rather than the grave.

And thither you went up to offer sacrifice is parallel to the previous two lines. Thither points back to the top of the mountain. You went up to offer sacrifice could refer figuratively to the cultic sexual activity mentioned in the previous line, or it could refer literally to the drink and cereal offerings mentioned in the previous verse.

Translation examples for this verse are:

• You have ritual sex on high mountains,
and you go there to offer sacrifices.

• You go on top of a high mountain [or, high mountains];
there you have sex with cult prostitutes and offer sacrifices.

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .