Fidei Donum §69

⁶⁹ In your dioceses zealously foster the Missionary Union of the Clergy, commended both by Our predecessors and by Ourselves. We have elevated it to the rank of a pontifical society so that no one may question the high opinion We have of it nor the great results We expect to be attained through its growth in membership. The efforts put forth by the pastors of the Church and by those who have been entrusted with mission work must be closely associated, since success depends largely upon unanimity of purpose.