9 “Turn away evil things unto mine enemies”. So however green they are, so however they flourish, for the fire they are being reserved. “In Your virtue destroy Thou them.” Because to wit they flourish now, because to wit they spring up like grass: do not thou be a man unwise and foolish, so that by giving thought to these things thou perish for ever and ever. For, “Turn Thou away evil things unto mine enemies.” For if you shall have place in the body of David Himself, in His virtue He will destroy them. These men flourish in the felicity of the world, perish in the virtue of God. Not in the same manner as they flourish, do they also perish: for they flourish for a time, perish for everlasting: flourish in unreal good things, perish in real torments. “In Your strength destroy,” whom in Your weakness You have endured.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)