Catechism of the Catholic Church §551 — excerpt
From the beginning of his public life Jesus chose certain men, twelve in number, to be with him and to participate in his mission. He gives the Twelve a share in his authority and 'sent them out to preach the kingdom of God and to heal."
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.