12 “You have turned My mourning into joy to Me”. Whom I, the Church, having received, the First-Begotten from the dead, now in the dedication of Your house, say, “You have turned my mourning into joy to me. You have put off my sackcloth, and girded me with gladness.” You have torn off the veil of my sins, the sadness of my mortality; and hast girded me with the first robe, with immortal gladness.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)