John Calvin Commentary Psalms 9:18

"For the needy shall not alway be forgotten, Nor the expectation of the poor perish for ever." — Psalms 9:18 (ASV)

For the poor shall not always be forgotten. The assertion that God will not forsake the poor and afflicted forever is a confirmation of the preceding sentence. By this, he implies that they may indeed seem to be forsaken for a time.

Let us, therefore, remember that God has promised His assistance to us, not by preventing our afflictions, but by eventually helping us after we have been long subdued under the cross.

David speaks expressly of hope or expectation, thereby encouraging us to prayer.

The reason God seems to take no notice of our afflictions is because He would have us awaken Him through our prayers. For when He hears our requests (as if He only then began to be mindful of us), He stretches out His powerful hand to help us.

David again repeats that this is not done immediately, so that we may persevere in hoping well, even though our expectations may not be instantly gratified.