58. It follows from this that the Sovereign Pontiff alone enjoys the right to recognize and establish any practice touching the worship of God, to introduce and approve new rites, as also to modify those he judges to require modification.[50] (Pius XII, Mediator Dei)
It furthermore declares, that this power has ever been in the Church, that, in the dispensation of the sacraments, their substance being untouched, it may ordain,--or change, what things soever it may judge most expedient, for the profit of those who receive, or for the veneration of the said sacraments, according to the difference of circumstances, times, and places. (Council of Trent, Sess. XXII Ch. II)
"The sacred pastors are not the inventors and composers of the Gospel, but merely the authorized guardians and preachers divinely established. Wherefore, we ourselves, and all bishops with us, can and must repat the words of Jesus Christ: "My teaching is not my own, but his who sent me" (John 7:16)....
"Therefore, we are not teachers of a doctrine born of the human mind, but we are in conscience bound to embrace and follow the doctrine which Christ Our Lord taught and which He solemnly commanded His Apostles and their successors to teach (Matthew 28:19-20)." (Encyclical Letter "Ad Sinarum Gentem," October 7, 1954)