30 Missionaries should remember that in preaching to the natives they must follow the same methods which the Divine Teacher used while He was on earth. Before He began to preach to the crowds, He first healed the sick: "and all that were sick he healed; and many followed him, and he healed them all: he had compassion on them, and healed their sick." ( Matt . viii, 16; Matt. xii, 15; Matt . xiv, 14) He commanded the Apostles to do likewise and bestowed upon them the power of healing: "And into what city so ever you enter . . . heal the sick that are therein, and say to them: The Kingdom of God is come nigh unto you," ( Luke x, 8, 9) and "going out they went about through the towns, preaching the gospel, and healing everywhere." ( Luke ix, 6) Neither should the missionary ever forget how kind and loving Jesus always showed Himself to babes and little children, or how when the apostles remonstrated with them, He bade them to "suffer little children to come unto Him." ( Matt . xix, 13, 14) Apropos of this, let Us recall what We said on another occasion, namely, that the missionaries who preach to the heathen know only too well how much good-will and real affection is gained for the Church by those who look after the health of the natives and care for their sick or who show a true love for their infants and children. All of which only goes to prove how readily the human heart responds to charity and to kindness.
Source: Rerum Ecclesiae (Vatican.va)