Charles Ellicott Commentary 1 Kings 15:13

"And also Maacah his mother he removed from being queen, because she had made an abominable image for an Asherah; and Asa cut down her image, and burnt it at the brook Kidron." — 1 Kings 15:13 (ASV)

An idol in a grove. The original word for “idol”—unique to this passage and its parallel, 2 Chronicles 15:16—appears to signify a “horrible abomination” of some monstrous kind. Instead of “in a grove,” we should read “for an asherah,” the wooden emblem of the Canaanite deity (for which, see 1 Kings 14:22). There seems little doubt that some obscene emblem is meant, of the kind so often connected with the worship of the productive powers of nature in ancient religions, substituted as a still greater abomination for the ordinary asherah.

Clearly, Maachah’s act was so flagrant that Asa took the unusual step—one the historian here greatly emphasizes—of degrading her in her old age from her high dignity, in addition to hewing down her idol and burning it publicly under the walls of Jerusalem.