7 Making no secret that this fate is a penalty inflicted for sin, he adds at once, “For we consume away in Your displeasure, and are troubled at Your wrathful indignation”: we consume away in our weakness, and are troubled from the fear of death; for we have become weak, and yet fearful to end that weakness. “Another,” says He, “shall gird you, and carry you whither you would not:” although not to be punished, but to be crowned, by martyrdom; and the soul of our Lord, transforming us into Himself, was sorrowful even unto death: for “the Lord's going out” is no other than in “death.”
8. “You have set our misdeeds before You”: that is, You have not dissembled Your anger: “and our age in the light of Your countenance.” “The light of Your countenance” answers to “before You,” and to “our misdeeds,” as above.
9. “For all our days are failed, and in Your anger we have failed”. These words sufficiently prove that our subjection to death is a punishment. He speaks of our days failing, either because men fail in them from loving things that pass away, or because they are reduced to so small a number; which he asserts in the following lines: “our years are spent in thought like a spider.” “The days of our age are threescore years and ten; and though men be so strong that they come to fourscore years, yet is more of them but labour and sorrow”. These words appear to express the shortness and misery of this life: since those who have reached their seventieth year are styled old men. Up to eighty, however, they appear to have some strength; but if they live beyond this, their existence is laborious through multiplied sorrows. Yet many even below the age of seventy experience an old age the most infirm and wretched: and old men have often been found to be wonderfully vigorous even beyond eighty years. It is therefore better to search for some spiritual meaning in these numbers. For the anger of God is not greater on the sins of Adam (through whom alone “sin entered into the world, and death by sin, and so death passed upon all men”), because they live a much shorter time than the men of old; since even the length of their days is ridiculed in the comparison of a thousand years to yesterday that is past, and to three hours: especially since at the very time when they provoked the anger of God to send the deluge in which they perished, their life was at its longest span.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)