Enflaming yourselves with idols under every green tree, slaying the children in the valleys under the clifts of the rocks?
Enflaming yourselves with idols - burning with lust toward idols (Gesenius); or else (cf. margin), in the terebinth groves, which the Hebrew х baa'eeliym (H410)] and the parallelism favour (note, Isaiah 1:29). If 'toward idols' were meant, after the Hebrew, haneechaamiym (H2552), there would probably have followed, to avoid confusion, not the Hebrew preposition [bª-], but the preposition х 'el (H413)], or the preposition lª-, especially since 'eeliym (H410) means terebinth trees as well as idols (Maurer). But the Chaldaic, Septuagint, Vulgate, Arabic, and Syriac support the English version.
Under every green tree - (2 Kings 17:10.) The tree, as in the Assyrian sculptures, was probably made an idolatrous symbol of the heavenly hosts.
Slaying the children - as a sacrifice to Moloch, etc. (2 Kings 17:31; 2 Chronicles 28:3.)
In the valleys - the valley of the son of Hinnom. Fire was put within a hollow brazen statue, and the child was put in his heated arms: kettle drums (Hebrew, top (H8596)) were beaten to drown the child's cries; whence the valley was called Tophet (2 Chronicles 33:6; Jeremiah 7:32).
Under the clifts of the rocks - the gloom of caverns suiting their dark superstitions.