There is apparently a series beginning here and extending to Psalm 50, in which the Head is addressed, and the various phenomena of his actings described, by the members of his body.
This Psalm, committed to the Sons of Korah, is the cry of David and any other true followers of the Lord, in times of trial, when the witnesses prophesy in sackcloth.
It is not so much a national Psalm, as one for the Church Universal, in as much as verses 17-22, humbly protest (what Israel as a nation could not) firm, unfaltering adherence to his name; and in Rom 8:36, are applied by Paul as expressive of the believer's state in a persecuting world.
Maschil is a musical reference.
It is the cry, or appeal, of the slaughtered sheep to their Shepherd. They begin by recalling his great deeds on behalf of his people coming out of Egypt. They lay all the stress of that deliverance on Himself, on his holy arm alone (v2). "You drove out the heathen!" etc.
This You is emphatic, similar to the use of the pronoun in Ezekiel 37:3, "You and none else know;" and then verse 5 "I, and none else, will cause the Spirit of life to enter you." Or like the pronoun (Rev 4:11), "For you, and non else, have created all things." Then in verse 5, there is an emphatic "O God, you are he: my King."
No less significant is the other monosyllable (v9) - "But you have cast off" -
The Selah pause (v8) had for a moment brought the harp to silence; and when its strings are touched again, it is to breathe forth lamentation. It seems to reverse the case stated in Leviticus 26:44, where are long tribulation there is hope of the removing of calamity introduce. Marked as golden, speaking as it does of a change to prosperity. All different here! The tide has ebbed, and no prospect of its coming in appears. We are sold for the most trifling sum, as if the master were only anxious to get his sheep off his hand (v12). We are a by-word (v14), and are put to shame by "the enemy and the avenger" whom you could so easily still (Psalm 8:2).
Yet, the sheep own no Shepherd but the LORD. Their protest is unreserved:
"You have broken us (and laid us helpless), in the place of dragons,
And covered us with the shadow of death,
If we have forgotten the name of the our God
Or (if) we have stretched out our hands to a strange God " -
We are cut off from society with our fellow men, we are thrust out into dens and caves, we flee to where serpents are the only inhabitants, we are lingering on the brink of the grave.
Yet, we can appeal "if we have forgotten!" This IF is a form of strong asseveration. It is the same form as our Lord uses in Luke 19:42. If you had known, then would blessing have come. It is like Exodus 32:32, "Yet now, if you will forgive their sin." It is like Psalm 95:7, "Today if you hear his voice" - then you shall enter rest.
Having made this protest, they add "Shall not God search this out:?" He knows all things. He knows we love Him. He knows that "our belly is grovelling on the earth" like the serpent.
"Awake, why do you sleep, O Lord?" (v23_
Hope dawns. Their God shall hear.
He allows them to awaken Him, and they in a manner cry through the curtains of his tent "Up, why do you sleep!" (Prayer book version.) The Banner of the Deliverer appears through the gloom. The sleeping Saviour awakes at the cry of his disciples, and is about to arise and still the storm "for his mercies' sake" (v26), - for the sake of the tender love he bears to them.
In the Latter Day we shall see, what is meant by this arising, in its fully glory. Such is this Psalm - The cry of the slaughtered sheep to the Shepherd.