This verse echoes, and with minor additions, repeats most of the words from verse 10.

And men shall enter the caves of the rocks: In verse 10 the prophet issued an order for people to “Enter into the rock” to escape from Yahweh’s terrifying judgment. New Revised Standard Version and Revised English Bible render the verb enter as an imperative in this verse also. Although the Hebrew form of the verb for enter here can be interpreted as an imperative, Hebrew Old Testament Text Project does not recommend it. In this context the verb introduces a statement of what will actually happen “in that day.” This fuller expression reveals the meaning of the short line “Enter into the rock” (see the comments on verse 10). The word for caves is an unusual one in Hebrew, but the Septuagint indicates that it refers to a hideout usually used by robbers. The caves of the rocks may be rendered “the hideouts in the mountains/rocks.”

And the holes of the ground: This pictures caves or openings in the ground. The Hebrew word for ground is rendered “dust” in verse 10. This word is usually translated “dust,” but in this context of holes it is better to say ground.

From before the terror of the LORD, and from the glory of his majesty: See the comments on verse 10.

When he rises to terrify the earth: This addition to the thought of verse 10 is repeated in verse 21. The pronoun he obviously refers to Yahweh, but this may need to be made explicit in some languages. The verb terrify comes from a different Hebrew root than the noun terror. To terrify the earth describes the purpose of Yahweh’s “rising,” but it does not simply mean to frighten people. It is rather a metaphor for punishment. Good News Translation and New International Version say “to shake the earth” (similarly New Jerusalem Bible), but readers may misunderstand this as referring to an earthquake. It is better to use a verb such as “judge” or “punish” here. The noun earth is an inclusive term, covering the world and those who live in it. The Hebrew for to terrify the earth is laʿaorts haʾarets, so there is a sound play here.

A translation example for this verse is:

• People will hide between the rocks
and in holes in the ground.
They will want to escape from Yahweh’s terrible punishment
and his overwhelming power,
when he appears in order to judge the world.

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .