Wilt thou show wonders to the dead! - מתים methim, dead men.
Shall the dead - רפאים rephaim, "the manes or departed spirits."
Arise and praise thee? - Any more in this life? The interrogations in this and the two following verses imply the strongest negations.
Wilt thou show wonders to the dead? - The wonders - or the things suited to excite admiration - which the living behold. Shall the dead see those things which here tend to excite reverence for thee, and which lead people to worship thee? The idea is that the dead will be cut off from all the privileges which attend the living on earth; or, that those in the grave cannot contemplate the character and the greatness of God. He urges this as a reason why he should be rescued. The sentiment here is substantially the same as in Psalm 6:5. See the notes at that passage. Compare Isaiah 38:18.
Shall the dead arise and praise thee? - The original word, here rendered “the dead,” is Rephaim - רפאים rephâ'iym On its meaning, see the notes at Isaiah 14:9. It means, properly, relaxed, languid, feeble, weak; and is then applied to the dead - the shades - the Manes - dwelling in the under-world in Sheol, or Hades, and supposed to be as shades or shadows, weak and feeble. The question here is not whether they would rise to live again, or appear in this world, but whether in Sheol they would rise up from their resting places, and praise God as men in vigor and in health can on the earth. The question has no reference to the future resurrection. It relates to the supposed dark, dismal, gloomy, inactive state of the dead.