Psalm 37:34 (NKJV)
Wait on the LORD, and keep His way. And He shall exalt you to inherit the land; When the wicked are cut off, you shall see it.
Waiting on the LORD is an act of faith; not to wait on Him is foolishness. David admits that the wicked might prosper, but he also affirms that they will not enjoy success forever. Just wait and see.