90 The call to mission derives, of its nature, from the call to holiness. A missionary is really such only if he commits himself to the way of holiness: "Holiness must be called a fundamental presupposition and an irreplaceable condition for everyone in fulfilling the mission of salvation in the Church." The universal call to holiness is closely linked to the universal call to mission . Every member of the faithful is called to holiness and to mission. This was the earnest desire of the Council, which hoped to be able "to enlighten all people with the brightness of Christ, which gleams over the face of the Church, by preaching the Gospel to every creature." The Church's missionary spirituality is a journey toward holiness. The renewed impulse to the mission ad gentes demands holy missionaries. It is not enough to update pastoral techniques, organize and coordinate ecclesial resources, or delve more deeply into the biblical and theological foundations of faith. What is needed is the encouragement of a new "ardor for holiness" among missionaries and throughout the Christian community, especially among those who work most closely with missionaries. Dear brothers and sisters: let us remember the missionary enthusiasm of the first Christian communities. Despite the limited means of travel and communication in those times, the proclamation of the Gospel quickly reached the ends of the earth. And this was the religion of a man who had died on a cross, "a stumbling block to Jews and folly to Gentiles"! (1 Cor 1:23) Underlying this missionary dynamism was the holiness of the first Christians and the first communities.
Source: Redemptoris Missio (Vatican.va)