59 From the bottom of Our heart, We call down upon the missions the worthy protection of their patrons and martyrs, and, first and foremost, the intercession of Mary, Mother and Queen of the Missions. With the greatest affection We impart to each one of you, Venerable Brethren, and to all those who in any way contribute to the propagation of God's kingdom, Our Apostolic Blessing. May it be a token and a pledge of the supernatural favors of the Eternal Father, who appeared to the world through His Son, the Savior of mankind, and may it kindle and multiply missionary zeal in the hearts of all. Given at Rome, at St. Peter's, on November 28, 1959, the second year of Our Pontificate.
Source: Princeps Pastorum (Vatican.va)