The Catholic Church received a mandate from Jesus Christ to "Go therefore and make disciples of all nations" (Matthew 28:19). This mandate has been observed by every generation of Christians, who have seen in it a clear mission to evangelize the entire world.
However, the work of missionaries is difficult, especially in areas of the world that are hostile to Christians.
During the last two centuries a renewed appreciation of missionaries has been fostered, especially with the institution of the Society of the Propagation of the Faith.
This society has worked hard to promote the missions and in 1926, petitioned Pope Pius XI to establish "a day of prayer and propaganda for the missions to be celebrated on the same day in every Catholic diocese, parish and institute in the world."
Pius XI responded favorably to their letter and promptly established the second to last Sunday of October to be, "Mission Sunday."
Mission Sunday
The original intention of this day, as stated in the letter the Society of the Propagation of the Faith gave to Pius XI, was so that "The day would foster understanding of the greatness of the missionary task, encourage zeal among the clergy and the people; offer an opportunity to make the APF ever more widely known and encourage offerings for the missions."
St. John Paul II confirmed this origin and intention in his message for World Mission Sunday in 1992, "World Mission Sunday, instituted in 1926 by Pope Pius XI at the request of the Society for the Propagation of the Faith, calls us each year in the spirit of the Church's unity and universality, to a renewed commitment to everyone's responsibility for the spread of the Gospel message."
Mission Sunday remains an important day in the Church's calendar year and continues to be celebrated in Catholic parishes around the world.