Melachim Bais 16:4

4 And he sacrificed and burnt ketoret in the [idolatrous] high places, and on the geva’ot, and under every spreading tree.

Melachim Bais 16:4 Meaning and Commentary

2 Kings 16:4

And he sacrificed and burnt incense in the high places, and on
the hills
Which none of the kings of Judah before him ever did; for though they connived at this practice in the people, they never encouraged it by their own example; and very probably he offered sacrifices there to idols, see ( 2 Chronicles 28:25 ) whereas the people sacrificed to the true God, though at a wrong place:

and under every green tree;
and which is never said of the people, and seems to confirm it, that Ahaz sacrificed to other gods, since the Heathens used to place idols under green trees, and worship them, whom the Jews imitated, ( Jeremiah 2:2 ) ( 3:6 ) .

Melachim Bais 16:4 In-Context

3 But he walked in the derech of the Melachim of Yisroel, and even made bno to pass through the eish, according to the to’avot of the Goyim, whom Hashem cast out from before the Bnei Yisroel.

4 And he sacrificed and burnt ketoret in the [idolatrous] high places, and on the geva’ot, and under every spreading tree.

5 Then Retzin Melech Aram (Syria) and Pekach Ben Remalyahu Melech Yisroel came up to Yerushalayim for milchamah; and they besieged Achaz, but could not overcome him.

6 At that time Retzin Melech Aram (Syria) recovered Eilat for Aram, and drove the Yehudim from Eilat; and the Edomim came to Eilat, and dwelt there unto this day.