Pascendi dominici gregis ("Feeding the Lord's Flock") is a Papal encyclical letter promulgated by Pope Pius X on 8 September 1907.
The pope condemned modernism and a whole range of other principles described as "evolutionary", which allowed change to Roman Catholic dogma. Pius X instituted commissions to cleanse the clergy of theologians promoting modernism and some of its (liturgical) consequences.
Traditionalist Catholics point to this document as evidence that pre-Vatican II popes were highly concerned about enemies of Christendom infiltrating the human element of the Catholic Church.
The encyclical was drafted by Joseph Lemius, procurator general of the Oblates of Mary Immaculate.
Pascendi dominici gregis enjoined a compulsory anti-modernist oath, introduced on 1 September 1910, which obliged all Catholic bishops, priests and teachers to come to clear terms with what they believed; this oath remained in force until Pope Paul VI abolished it in 1967. When the Congregation for the Doctrine of the Faith, under the authority of Pope John Paul II, mandated the use of a new Oath of Fidelity in 1989, some theologians labeled it as a new kind of anti-modernist oath.