John Gill Commentary 2 Chronicles 17:6

"And his heart was lifted up in the ways of Jehovah: and furthermore he took away the high places and the Asherim out of Judah." — 2 Chronicles 17:6 (ASV)

And his heart was lifted up in the ways of the Lord
It was engaged in them, was bent and set upon them; he walked in them with great pleasure and cheerfulness, being inspired with zeal and courage; he was fearless and intrepid, and regarded not any opposition he might have, or expect to have, in the work of reformation in which he was concerned:

moreover, he took away the high places ;
such as were dedicated to idols, but not those in which the true God was worshipped, (2 Chronicles 20:33)

and groves out of Judah ;
where idols were placed; for though these had been removed by Asa, yet had been renewed in the latter part of his days, when more negligent of religion.