12 “They have set against Heaven their mouth, and their tongue has passed over above the earth”. For this, “has passed over above the earth” is, they pass over all earthly things? What is it to pass over all earthly things? He does not think of himself as a man that can die suddenly, when he is speaking; he does menace as if he were always to live: his thought does transcend earthly frailty, he knows not with what sort of vessel he is enwrapped; he knows not what has been written in another place concerning such men: “His spirit shall go forth, and he shall return unto his earth, in that day shall perish all his thoughts.” But these men not thinking of their last day, speak pride, and unto Heaven they set their mouth, they transcend the earth.
If a robber were not to think of his last day, that is, the last day of his trial, when sent to prison, nothing would be more monstrous than he: and yet he might escape. Whither do you flee to escape death? Certain will that day be. What is the long time which you have to live? How much is the long time which has an end, even if it were a long time? To this there is added that it is nought: and the very thing which is called long time is not a long time, and is uncertain. Why does he not think of this? Because he has set against Heaven his mouth, and his tongue has passed over above the earth. “And full days shall be found in them.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)