מלכים א, פרק י״ד, פסוק כ״ג

The Kingdom of Judah's descent into false worship was driven by a deep cultural desire to assimilate rather than any political necessity. After all, the Temple stood right in their midst [ביאור שטיינזלץ]. The people actively chose to build these centers of worship in direct imitation of the ten tribes in the neighboring Kingdom of Israel [רש״י, מצודת דוד].

To this end, three distinct types of worship sites were established across the land. The first were high places, which were tall structures supporting altars meant for foreign worship [מצודת ציון]. Constructing these was a severe offense; once the Temple was built, such high places were strictly forbidden, even if the sacrifices offered upon them were directed to God [רלב״ג]. The second type were pillars, consisting of altars formed from a single stone [מצודת ציון]. The Torah explicitly banned setting up these stone pillars, even if they were dedicated to God [רלב״ג]. Finally, they created Asherim, which were idols closely associated with trees [רלב״ג].

These sites were scattered across the landscape, specifically placed on high hills and beneath leafy, moist trees with thick, spreading branches [מצודת ציון]. The exact arrangement of these worship centers is understood in different ways. One approach suggests that the high places were built on hills to mimic the ancient customs of the nations that had been driven out of the land, while the Asherim were positioned under trees because they were carved directly from the wood [רלב״ג]. Conversely, other commentators suggest a crossed arrangement of the locations, explaining that the hills were actually the designated spots for the Asherim, while the high places and stone pillars were set up beneath the shade of the trees [מלבי״ם, מצודת דוד].