9 But men (who doubtless are many) who follow after things temporal, know not to say anything else, than, “Who shows us good things?” when the true and certain good within their very selves they cannot see. Of these accordingly is most justly said, what he adds next: “From the time of His grain, of wine, and oil, they have been multiplied.” For the addition of His, is not superfluous. For the grain is God's: inasmuch as He is “the living bread which came down from heaven.” The wine too is God's: for, “they shall be inebriated,” he says, “with the fatness of your house.” The oil too is God's: of which it is said, “You have fattened my head with oil.” But those many, who say, “Who shows us good things?” and who see not that the kingdom of heaven is within them: these, “from the time of His grain, of wine, and oil, are multiplied.”
For multiplication does not always betoken plentifulness, and not, generally, scantiness: when the soul, given up to temporal pleasures, burns ever with desire, and cannot be satisfied; and, distracted with manifold and anxious thought, is not permitted to see the simple good. Such is the soul of which it is said, “For the corruptible body presses down the soul, and the earthly tabernacle weighs down the mind that muses on many things.” A soul like this, by the departure and succession of temporal goods, that is, “from the time of His grain, wine, and oil,” filled with numberless idle fancies, is so multiplied, that it cannot do that which is commanded, “Think on the Lord in goodness, and in simplicity of heart seek Him.” For this multiplicity is strongly opposed to that simplicity.
And therefore leaving these, who are many, multiplied, that is, by the desire of things temporal, and who say, “Who shows us good things?” which are to be sought not with the eyes without, but with simplicity of heart within, the faithful man rejoices and says, “In peace, together, I will sleep, and take rest”. For such men justly hope for all manner of estrangement of mind from things mortal, and forgetfulness of this world's miseries; which is beautifully and prophetically signified under the name of sleep and rest, where the most perfect peace cannot be interrupted by any tumult.
But this is not had now in this life, but is to be hoped for after this life. This even the words themselves, which are in the future tense, show us. For it is not said, either, I have slept, and taken rest; or, I do sleep, and take rest; but, “I will sleep, and take rest.” Then shall “this corruptible put on incorruption, and this mortal shall put on immortality; then shall death be swallowed up in victory.” Hence it is said, “But if we hope for that we see not, we wait in patience.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)