VATICAN CITY — “Being a Christian ... is a life in union with Christ,” and true evangelization stems directly from this spiritual bond, Pope Leo XIV said in a special message for the 100th anniversary of World Mission Day, Oct. 18.

"The more united we are in Christ, the better able we will be to carry out together the mission that he entrusts to us," the pope wrote. “This spirituality constitutes the daily expression of missionary discipleship."

Leo himself served for years in Peru as an Augustinian missionary priest and bishop, and has often called on Catholics “to proclaim the Gospel without fear, to be missionaries.”

Pope Pius XI established World Mission Day in 1926, following the publication of his landmark encyclical Rerum Ecclesiae, which promoted the idea that supporting missions was the responsibility of all Catholics.

The centennial observance will be marked by Masses all over the world, with the pontiff celebrating the canonization of seven blesseds on Oct. 19 in St. Peter’s Basilica.

In his message, the pope highlighted historical figures of faith, including Blessed Pauline Marie Jaricot, who established the Association of the Living Rosary 200 years ago to mobilize prayer and support for missionaries.

The pope urged the faithful to draw inspiration from the zeal of St. Therese of the Child Jesus. Until death and beyond, she declared that she would continue her mission: “I shall desire in heaven the same thing as I do now on earth: to love Jesus and to make him loved.”

“If unity is the condition of mission, love is its essence,” the pope wrote. “Let us commit to contributing to the great mission of evangelization — which is a work of love.”