These verses repeat that Yahweh will humble the haughty and destroy the idols; idol worshippers and the haughty will seek refuge in caves and rocks. Verses 20–21 suggest that the idol worshippers will also attempt to provide refuge for their idols by taking them into the caves with them. However, Isaiah points out that idols are no more effective in the caves than on the hills. Although these false gods attempt to hide from Yahweh, he will still destroy them. In verse 20, casting the idols to the “moles and to the bats” refers to the underground lairs of each.
Comparison: Verse 21 reverses a phrase from Isaiah. In Isaiah 2:21 we have “the glory of his majesty.” The Book of Mormon text has “the majesty of his glory.” Skousen suggests that this is an early transmission error but that the reversed phrase also makes sense.