The Papal Bull of Saint Pope Pius V granting in perpetuity the right of every priest use the venerable and traditional Latin Missal in offering Holy Mass. Issued July 14, 1570.
Rorate Caeli: [From the very first, upon Our elevation to the chief Apostleship], We gladly turned our mind and energies and directed all out thoughts to those matters which concerned the preservation of a pure liturgy, and We strove with God’s help, by every means in our power, to accomplish this purpose. For, besides other decrees of the sacred Council of Trent, there were stipulations for Us to revise and re-edit the sacred books: the Catechism, the Missal and the Breviary. Read the rest of the Papal Bull here.