9 “One He humbles, and another He exalts”. Whom humbles, whom exalts this Judge? Observe these two men in the temple, and you see whom He humbles and whom He exalts. “They went up into the Temple to pray,” He says, the one a Pharisee, and the other a Publican....“Verily I say unto you, that Publican went down justified more than that Pharisee: for every one that exalts himself shall be humbled; and he that humbles himself shall be exalted.” Thus has been explained a verse of this Psalm. God the Judge does what? “One He humbles, and another He exalts:” He humbles the proud, He exalts the humble.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)