24 The mission of the Church, like that of Jesus, is God's work or, as Luke often puts it, the work of the Spirit. After the resurrection and ascension of Jesus, the apostles have a powerful experience which completely transforms them: the experience of Pentecost. The coming of the Holy Spirit makes them witnesses and prophets (cf. Acts 1:8; 2:17-18). It fills them with a serene courage which impels them to pass on to others their experience of Jesus and the hope which motivates them. The Spirit gives them the ability to bear witness to Jesus with "boldness." When the first evangelizers go down from Jerusalem, the Spirit becomes even more of a "guide," helping them to choose both those to whom they are to go and the places to which their missionary journey is to take them. The working of the Spirit is manifested particularly in the impetus given to the mission which, in accordance with Christ's words, spreads out from Jerusalem to all of Judea and Samaria, and to the farthest ends of the earth. The Acts of the Apostles records six summaries of the "missionary discourses" which were addressed to the Jews during the Church's infancy (cf. Acts 2:22-39; 3:12-26; 4:9-12; 5:29-32; 10:34-43; 13:16-41). These model speeches, delivered by Peter and by Paul, proclaim Jesus and invite those listening to "be converted," that is, to accept Jesus in faith and to let themselves be transformed in him by the Spirit. Paul and Barnabas are impelled by the Spirit to go to the Gentiles (cf. Acts 13:46-48), a development not without certain tensions and problems. How are these converted Gentiles to live their faith in Jesus? Are they bound by the traditions of Judaism and the law of circumcision? At the first Council, which gathers the members of the different churches together with the apostles in Jerusalem, a decision is taken which is acknowledged as coming from the Spirit: it is not necessary for a Gentile to submit to the Jewish Law in order to become a Christian (cf. Acts 15:5-11, 28). From now on the Church opens her doors and becomes the house which all may enter, and in which all can feel at home, while keeping their own culture and traditions, provided that these are not contrary to the Gospel.
Source: Redemptoris Missio (Vatican.va)