9 “Behold, you have made my days old”. For these days are “waxing old.” I long for new days “that never shall wax old,” that I may say, “Old things have passed away; behold, things have become new.” Already new in hope; then in reality. For though, in hope and in faith, made new already, how much do we even now do after our old nature! For we are not so completely “clothed upon” with Christ, as not to bear about with us anything derived from Adam. Observe that Adam is “waxing old” within us, and Christ is being “renewed” in us. “Though our outward man is perishing, yet is our inward man being renewed day by day.” Therefore, while we fix our thoughts on sin, on mortality, on time, that is hastening by, on sorrow, and toil, and labour, on stages of life following each other in succession, and continuing not, passing on insensibly from infancy even to old age; while, I say, we fix our eyes on these things, let us see here “the old man,” the “day that is waxing old;” the Song that is out of date; the Old Testament; when however we turn to the inner man, to those things that are to be renewed in place of these which are to be changed, let us find the “new man,” the “new day,” the “new song,” the “New Testament;” and that “newness,” let us so love, as to have no fears of its “waxing old.”...This man, therefore, who is hasting forward to those things which are new, and “reaching forward to those things which are before,” says, “Lord, make me to know mine end, and the number of my days, which really is, that I may know what is wanting unto me.” See he still drags with him Adam; and even so he is hasting unto Christ. “Behold,” says he, “you have made my days old.” It is those days that are derived from Adam, those days, I say, that you have made old. They are waxing old day by day: and so waxing old, as to be at some day or other consumed also. “And my substance is as nothing before You.” “Before You, O Lord, my substance is as nothing.” “Before You;” who see this; and I too, when I see it, see it only when “before You.”
When “before men” I see it not. For what shall I say? What words shall I use to show, that which I now am is nothing in comparison of That which truly “IS”? But it is within that it is said; it is within that it is felt, so far as it is felt. “Before You, O Lord,” where Your eyes are; and not where the eyes of men are. And where Your eyes are, what is the state of things? “That which I am is as nothing.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)