Liturgical reforms of Pope Pius XII

In 1953, by the apostolic constitution Christus Dominus, he continued to require not ingesting from midnight before receiving communion, but ruled that water did not break the fast.

He also relaxed the fasting requirement for the sick and travelers, those engaged in exhausting physical labor, and priests who celebrate several Masses on the same day.

[3] Under Pius XII, the Sacred Congregation of Rites granted permission for the use of local languages in countries with expanding Catholic mission activities, including in Indonesia and Japan in 1941–2.

All such permissions, however, were to be granted by the Holy See, and Pius XII strongly condemned the efforts of individual priests and communities to introduce the vernacular on their own authority.

[8] Pius XII also instituted the feast of the Immaculate Heart of Mary, which he established as a double of the second class and fixed to August 22, the octave day of the Assumption.

A major innovation occurred with the incorporation of renewal of baptismal promises by the entire congregation, "a milestone" that introduced modern languages into the general Roman liturgy for the first time.

[22] Other Christian denominations adopted the popular Roman Catholic Easter ceremonies in later years, an ecumenical influence of Pius XII.

In addition to the new Easter Vigil, modified on an experimental basis in 1951 and now made permanent, he promulgated the rites for Palm Sunday, Holy Thursday and Good Friday, the most important ceremonies in the Roman liturgy.

Pius had already, in 1949, made a public declaration that the Latin word "perfidus", which is applied to the Jewish people in this prayer, means "unbelieving", not "perfidious" or "treacherous".

[26] As the Liturgical Movement had long been exploring the history and form of concelebrating Mass, in 1956, Pius specified that all celebrants say the words of consecration aloud if they mean to participate fully, not just externally.