Council of Trent
there is a Purgatory, and that the souls there detained are helped by the suffrages of the faithful, but principally by the acceptable sacrifice of the altar.
Source details
1563 · Session XXV — Decree Concerning Purgatory
Checked word-for-word against The Canons and Decrees of the Sacred and Oecumenical Council of Trent · 2026-07-17