Catechism of the Catholic Church
425 The transmission of the Christian faith consists primarily in proclaiming Jesus Christ in order to lead others to faith in him. From the beginning, the first disciples burned with the desire to proclaim Christ: "We cannot but speak of what we have seen and heard." 11 It And they invite people of every era to enter into the joy of their communion with Christ:
That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked upon and touched with our hands, concerning the word of life - the life was made manifest, and we saw it, and testify to it, and proclaim to you the eternal life which was with the Father and was made manifest to us- that which we have seen and heard we proclaim also to you, so that you may have fellowship with us; and our fellowship is with the Father and with his Son Jesus Christ. And we are writing this that our joy may be complete. 12
English Translation of the Cathechism of the Catholic Church for the United States of America © 1997, United States Catholic Conference, Inc.