(On this matter of the Pelagians) two Councils have already been sent to
the Apostolic See; and from there rescripts too have come. The matter is at
an end; would that the error too might some time be at an end.
St. Peter Chrysologus, Letter to Eutyches 25, 2 (449 AD)
We exhort you in every respect, honorable brother, to heed obediently
what has been written by the Most Blessed Pope of the City of Rome; for
Blessed Peter, who lives and presides in his own see, provides the truth of
faith to those who seek it. For we, by reason of our pursuit of peace and
faith, cannot try cases on the faith without the consent of the Bishop of the
City of Rome.
Catechism of the Council of Trent (1566)
Pt. I, Ch. X: So has (Christ) placed over His Church, which He governs
by His invisible Spirit, a man to be His vicar and the minister of His power.
A visible Church requires a visible head; therefore the Savior appointed
Peter head and pastor of all the faithful, when He committed to his care the
feeding of all His sheep, in such ample terms that He willed the very same
power of ruling and governing the entire Church to descend to Peters
successors.
Catechism of the Catholic Church (1992)
No. 891:
The Roman Pontiff, head of the college of bishops, enjoys
this infallibility in virtue of his office, when, as supreme pastor and teacher
of all the faithfulwho confirms his brethren in the faith he proclaims
by a definitive act a doctrine pertaining to faith or morals ... The
infallibility promised to the Church is also present in the body of bishops
when, together with Peters successor, they exercise the supreme
Magisterium, above all in an Ecumenical Council. When the Church
through its supreme Magisterium proposes a doctrine for belief as being