22 See who this is: David as one man was seeming to implore; see ye here our image and the type of the Church.
“Deal kindly, O Lord, in Your good will with Sion”. With this Sion deal kindly. What is Sion? A city holy. What is a city holy? That which cannot be hidden, being upon a mountain established. Sion in prospect, because it has prospect of something which it hopes for. For Sion is interpreted “prospect,” and Jerusalem, “vision of peace.” You perceive then yourselves to be in Sion and in Jerusalem, if being sure ye look for hope that is to be, and if you have peace with God. “And be the walls of Jerusalem built.” “Deal kindly, O Lord, in Your good will with Sion, and be the walls of Jerusalem built.” For not to herself let Sion ascribe her merits: do Thou with her deal kindly, “Be the walls of Jerusalem built:” be the battlements of our immortality laid, in faith and hope and charity.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)