9 The sacred liturgy does not exhaust the entire activity of the Church. Before men can come to the liturgy they must be called to faith and to conversion: "How then are they to call upon him in whom they have not yet believed? But how are they to believe him whom they have not heard? And how are they to hear if no one preaches? And how are men to preach unless they be sent?" (Rom. 10:14-15). Therefore the Church announces the good tidings of salvation to those who do not believe, so that all men may know the true God and Jesus Christ whom He has sent, and may be converted from their ways, doing penance . To believers also the Church must ever preach faith and penance, she must prepare them for the sacraments, teach them to observe all that Christ has commanded , and invite them to all the works of charity, piety, and the apostolate. For all these works make it clear that Christ's faithful, though not of this world, are to be the light of the world and to glorify the Father before men.
Source: Sacrosanctum Concilium (Vatican.va)