Albert Barnes Commentary Isaiah 38:18

"For Sheol cannot praise thee, death cannot celebrate thee: They that go down into the pit cannot hope for thy truth." — Isaiah 38:18 (ASV)

For the grave cannot praise thee - The Hebrew word here is Sheol. It is put by metonymy here for those who are in the grave, that is, for the dead.

The word praise here evidently refers to the public and solemn celebration of God’s goodness.

It is clear, I think, that Hezekiah believed in a future state, or expected to dwell with the inhabitants of the land of silence (Isaiah 38:11) when he died.

However, he did not regard that state as one suited for celebrating God’s public praises. It was a land of darkness, an abode of silence and stillness, a place with no temple and no public praise like he had been accustomed to.

A similar sentiment is expressed by David in Psalm 6:5:

For in death there is no remembrance of thee;
In the grave who shall give thee thanks?

Regarding the Jewish conceptions of the state of the dead, see the notes at Isaiah 14:15 and Isaiah 14:19.

(See the Supplementary note at Isaiah 14:9; also the Prefatory Remarks by the Editor on the Author’s exposition of Job. The ideas held by the Author on the state of knowledge among the ancient saints regarding a future world must be regarded as especially unfortunate. Following the fashion of some German critics, the Old Testament figures are reduced to the same level as the heroes of Homer and Virgil, at least as far as this matter is concerned.)

Cannot hope for thy truth - They are shut out from all the means by which your truth is brought to the mind and the offers of salvation are presented.

Their probation is at an end; their privileges are closed; their destiny is sealed up.

The idea is that it is a privilege to live, because this is a world where the offers of salvation are made, and where those who are conscious of guilt may hope in God’s mercy.