49 It is necessary first and foremost to strive to establish Christian communities everywhere, communities which are "a sign of the presence of God in the world" and which grow until they become churches. Notwithstanding the high number of dioceses, there are still very large areas where there are no local churches or where their number is insufficient in relation to the vastness of the territory and the density of the population. There is still much to be done in implanting and developing the Church. This phase of ecclesial history, called the plantatio Ecclesiae , has not reached its end; indeed, for much of the human race it has yet to begin. Responsibility for this task belongs to the universal Church and to the particular churches, to the whole people of God and to all its missionary forces. Every church, even one made up of recent converts, is missionary by its very nature, and is both evangelized and evangelizing. Faith must always be presented as a gift of God to be lived out in community (families, parishes, associations), and to be extended to others through witness in word and deed. The evangelizing activity of the Christian community, first in its own locality, and then elsewhere as part of the Church's universal mission, is the clearest sign of a mature faith. A radical conversion in thinking is required in order to become missionary, and this holds true both for individuals and entire communities. The Lord is always calling us to come out of ourselves and to share with others the goods we possess, starting with the most precious gift of all - our faith. The effectiveness of the Church's organizations, movements, parishes and apostolic works must be measured in the light of this missionary imperative. Only by becoming missionary will the Christian community be able to overcome its internal divisions and tensions, and rediscover its unity and its strength of faith. Missionary personnel coming from other churches and countries must work in communion with their local counterparts for the development of the Christian community. In particular, it falls to missionary personnel - in accordance with the directives of the bishops and in cooperation with those responsible at the local level - to foster the spread of the faith and the expansion of the Church in non-Christian environments and among non-Christian groups, and to encourage a missionary sense within the particular churches, so that pastoral concern will always be combined with concern for the mission ad gentes . In this way, every church will make its own the solicitude of Christ the Good Shepherd, who fully devotes himself to his flock, but at the same time is mindful of the "other sheep, that are not of this fold." (Jn 10:16)
Source: Redemptoris Missio (Vatican.va)