Charles Ellicott Commentary 2 Kings 16:4

"And he sacrificed and burnt incense in the high places, and on the hills, and under every green tree." — 2 Kings 16:4 (ASV)

In the high places. —These are evidently distinguished from “the hills,” as two different prepositions are used in the Hebrew, just as in English. A bâmâh, or “high-place,” was a local sanctuary, and it appears that a sacred pillar or altar might be called a bâmâh. Mesha king of Moab speaks of his pillar as “this bâmath” (See Note on 2 Kings 1:1.)

Under every green tree. —Compare 1 Kings 14:23; Hosea 14:8. Thenius says not so much a green as a thick-foliaged and shadow-yielding tree. They burn incense ... under oaks, and poplars, and teil trees, because the shadow thereof is good (Hosea 4:13).

THE SYRO-EPHRAIMITIC WAR, AND THE INTERVENTION OF TIGLATH PILESER. (Compare Isaiah 7:1 to Isaiah 9:7, “an epitome of the discourses delivered by the prophet at this great national crisis.”—Cheyne.)