BBC: Psalm 9:15-20
15 The nations have sunk in the pit that they made;
in the net that they hid, their own foot has been caught.
16 The Lord has made himself known; he has executed judgment;
the wicked are snared in the work of their own hands. Higgaion. Selah
17 The wicked shall return to Sheol,
all the nations that forget God.
18 For the needy shall not always be forgotten,
and the hope of the poor shall not perish forever.
19 Arise, O Lord! Let not man prevail;
let the nations be judged before you!
20 Put them in fear, O Lord!
Let the nations know that they are but men! Selah
In the climax of this psalm proclaiming the awesome righteous judgment and reign of God, the psalmist highlights the social ramifications of rejecting God. This is not an individualistic rejection but a widespread refusal (Rom 1:18-31). The result is failure in one’s own work (v. 15). While the world will succeed in setting up their rejection of God, it will then enclose upon them and all in fulfillment of the very judgment of God (v. 16).
Knowing these things to be true, the psalmist is able to pray that they be brought about now (v. 19). With judgment comes fear and knowledge (v. 20). For salvation to come judgment must come followed by swift repentance.